One of Italy's largest engineering unions has called for a four-hour strike against Prime Minister Mario Monti's labor reforms.

The Unione Italiana Lavoratori Metalmeccanici (UILM), which is affiliated with the 2.2 million-strong Unione Italiana del Lavoro (UIL), said they were calling the strike to protest proposed changes to labor laws which will make it easier for firms to fire workers during hard business times.

The statement follows growing resentment among Italy's unions towards the reforms, with the country's Italian General Confederation of Labour (CGIL) union recently announcing its own set of 16-hour stoppages.

It is not clear yet when the strikes are set to go ahead.

Unions are angry at changes to Article 18 of the labor statute, which the government says has created a large number of mainly younger workers on unsecure, temporary contracts.

According to the Monti coalition, firms are scared of hiring workers on full-time contracts as it is extremely hard to fire them during lean economic times.

The left-leaning Democratic Party, a coalition partner of the Monti government, has also called for the scrapping of proposals to remove the automatic right to reinstate workers found to have been unjustly laid off.

Critics of the reforms say they do little to adjust the so-called dual labor market, and offer little to discourage the use of cheap labor.

The issue has dented Monti's approval ratings, with a survey in the Italian daily La Repubblica showing the prime minister's approval rating had fallen from 59 percent to 55 percent, according to Reuters.