Chancellor George Osborne should focus on implementing the growth-boosting measures he unveiled last year in the budget due on March 21, Britain's biggest business lobby group said on Wednesday.

The Confederation of British Industry also railed against calls by the opposition Labour party for a temporary cut in value-added tax to boost demand, saying it would send the wrong signal to markets after Moody's warned Britain that its triple-A rating was at risk.

In a letter to Osborne setting out its wish-list for the budget, the CBI urged the government to consider changes to the tax system to encourage investment in infrastructure among other measures that it said would cost just 500 million pounds a year to implement.

It also asked Osborne to press ahead with plans he unveiled in November to encourage pension funds to invest in infrastructure, as well as to deliver on a 20 billion pound credit easing scheme to help small and medium-sized enterprises.

The Chancellor must use this budget to score the growth and investment policy goals he put forward in the Autumn Statement, said CBI Director General John Cridland.

In the first three months of this year we're in delivery mode, not new ideas mode, he said.

Official data on Tuesday showed the government looked set to beat its deficit-cutting target for the 2011/12 fiscal year.

Figures showing Britain racked up the highest surplus in four years in January fuelled demands from the opposition Labour party as well as from within the Conservative-Liberal Democrat coalition for Osborne to relent on the pace of fiscal austerity.

Labour finance spokesman Ed Balls has called for a temporary cut in value-added sales tax to boost demand, at a cost to the exchequer of 12 billion pounds a year.

The CBI chief said that risked provoking the ire of financial markets, while raising infrastructure spending could boost the economy by three times as much.

Following Moody's outlook, increasing borrowing levels does not seem to be the best way of increasing confidence in international money markets that the UK is a good place to invest, Cridland said. The negative outlook is clearly a signal that while we do have a credible plan, we're not home and dry.

(Reporting by Fiona Shaikh)