In case there was any doubt about the ideology of Germany's Left Party, its leaders have brought out a cookbook that includes such favourites as anti-Atomic waffles and Soljanka, a feisty Russian soup that was popular in communist East Germany.

Hardly subversive. Even Chancellor Angela Merkel admits to Ostalgie (nostalgia for the German Democratic Republic, where she grew up) when it comes to the soup.

But apparently the Left are still deemed enough of a threat to the German constitution that everything their top lawmakers say or write - perhaps even the cookbook - is worthy of surveillance by the state.

Germany's domestic intelligence agency in January confirmed it has more than a third of the Left's 76 MPs in the Bundestag (lower house of parliament) under surveillance as part of its job keeping tabs on any group suspected of harbouring views, or associating with people who harbour views, that could be construed as anti-constitutional because they question the basic tenets of Germany's parliamentary democracy.

They haven't understood that the Cold War is over, said Gregor Gysi, who began his career in East Germany's Socialist Unity Party (SED), the Left's predecessor, and finds himself still under suspicion more than two decades after reunification.

It had long been an open secret that the government kept close tabs on some of the more hardline Left MPs, but the revelation that no fewer than 27 elected lawmakers from the party - including parliamentary leader Gysi, a deputy speaker of parliament and other moderates - were being watched has led to widespread criticism and scrutiny of the Federal Office for the Protection of the Constitution's (BvF) work.

The news compared unfavourably with the failure of the BvF and other agencies to combat right-wing violence - in particular a 10-year anti-immigrant murder spree by a small neo-Nazi cell that police stumbled across last November in Zwickau in east Germany.

Centre-right and centre-left lawmakers are now questioning the priorities of the security services and asking whether leftist MPs like Gysi pose such a threat to public order that federal agents should be assigned keep watch on them full-time.

The revelations have created a rare wave of solidarity for a party that in the west is ignored or reviled as extremist.

The manner in which the Left Party is being observed is not acceptable, said Siegfried Kauder, conservative chairman of the Bundestag's legal affairs committee. After all, parliament is supposed to monitor the constitution; the Office for the Protection of the Constitution does not monitor parliament.

Many politicians echo his concern about parliament being undermined - a serious charge in Germany, whose experience of totalitarianism makes it acutely aware of the need for checks and balances and transparency when it comes to executive powers.

The Left has challenged the legality of the surveillance, which the Constitutional court is expected to rule on this year.

PEACEFUL? OR DESTRUCTIVE

The centre-left Social Democrats (SPD) and Greens still generally keep their distance from the Left, and one senior MP from Merkel's party, who spoke on condition of anonymity, said the party was deeply destructive and had to be watched.

Speaking at his legal practice in west Berlin, where clients have to ask if they can speak freely, Gysi said it was natural that he should have been viewed with suspicion in the immediate aftermath of the fall of the Berlin Wall.

But the ideology of the Left today is peaceful, democratic and social, and not a threat to the constitution, said Gysi.

The main platforms of the party, which represents about a tenth of German voters, are welfare reforms, an end to overseas military missions and more investment in depressed areas of the former East Germany where most of its followers live.

Show me where the constitution says we are obliged to have a capitalist economic system, he said.

The interior ministry and the BvF argue that it is only fulfilling its legal obligations - reinforced by a federal court ruling from 2010 - and cites the hardline views of Left factions like the Communist Platform and what it says are documented contacts between Left politicians and foreign terrorist organisations, such as the militant Kurdistan Workers Party.

The law says that if there are grounds to suspect a party has extremist tendencies then our office has to place it under surveillance. Under the law there is no choice, said national BvF chief Heinz Fromm in a recent interview on national radio.

The surveillance methods used are not intrusive - no wiretaps, tailing, informants or other classics of the spy genre - but use information also available to academics and the media, said a security source speaking on condition of anonymity.

But in the federal structure of Germany's security services, some states say they have opted for full intelligence methods - such as wiretaps and informants - to monitor the Left.

In the conservative heartland of Bavaria, applicants for civil service posts like police and teachers are prohibited from membership of extremist organisations - including the Left.

Forming coalitions with the Left at federal level or co-sponsoring bills with them in the Bundestag has been taboo, though there have there have been power-sharing deals with the SPD in state assemblies in the east, including Berlin until last year, and the main parties have decided to con-sponsor a bill with the Left on the Zwickau neo-Nazis.

Alexander Dobrindt, secretary-general of Bavaria's Christian Social Union - the sister party of Merkel's Christian Democrats (CDU) - goes further, saying the Left's very disturbed relationship with our free democratic order means it ought to be banned outright.

This equates the Left with the right-wing extremists of the German National Democratic Party (NPD), which is threatened with a ban for its links to the Zwickau cell.

Sebastian Edathy, an SPD politician chairing a panel looking into the German security services' failure to stop the neo-Nazi killers, sees grounds for outlawing the NPD but not the Left.

On the fringes of the Left there are people who cannot be persuaded to conform to the structure of our democratic state of law. But that doesn't mean the whole party should be suspect and

a third of its MPs put under surveillance, he said.

The Left complains that conservatives are just abusing state resources to destabilise our voter base and incriminate us politically, said Wolfgang Neskovic, an independent MP allied to the Left who is a former federal court judge.

I understand we are uncomfortable for the conservatives, but they should thrash it out politically instead of using the intelligence agency to stigmatise us, he told Reuters.

POLITICAL CULTURE

Politics professor Gero Neugebauer sees the treatment of the Left as part a political culture dating back to West Germany's ban of the communist party in 1956. The prohibition was later narrowed to only groups suspected of links to the GDR, but anti-communism has pervaded the centre-right and centre-left.

Germany's conservatives lost their enemy in 1990 and had to reconstruct one. But they're doing the Left a favour by putting pressure on it and creating something like solidarity, he said.

Neugebauer, a teacher at Berlin's Free University, said the MPs under surveillance were mainly former East Germans with a pragmatic outlook, campaigning for social change - on issues like unemployment and pensions - within the constitution.

When the Greens burst onto Germany's political scene in the 1980s, some of their radical anti-nuclear, ecologist and feminist firebrands also attracted the attention of the security services. But they managed to make their appeal mainstream in less than two decades and have now held power on the national and regional level, with especially strong support among well-educated, prosperous, middle-class Germans - unlike the Left.

While disapproving of the wholesale surveillance of MPs, the main opposition sticks to its public position that the Left is unfit to govern.

The party argues that labelling it as extremist discourages the kind of moderate membership that would help it integrate.

A police officer or teacher in Bavaria won't want to be a member of the Left Party, said Gysi.

So we'll only get members who aren't bothered about being watched by the intelligence service - and that will change our political structure.

(Editing by Sonya Hepinstall)