LONDON (Reuters) –- Britain's biggest public sector trade union said yesterday it would fight government attempts to impose a pay freeze and curb pensions for its members.

Deputy Prime Minister Nick Clegg said on Monday that Britain could no longer afford "gold-plated" public sector pensions and would have to examine the annual £160 billion ($235 billion) bill for public sector pay.

The government will set out on June 22 its plans to cut a deficit running at around 11 percent of national output. There are fears of confrontations with unions once cuts start to bite later in the year.

"We will give our full support to any branch that is forced to resort to industrial action to defend jobs," Unison general secretary Dave Prentis told the union's annual conference. Unison has more than 1.3 million members.

The Conservatives, who are in coalition with Clegg's smaller Liberal Democrats, have pledged to freeze pay for five out of six million public sector workers for a year from 2011.

Employers' group the CBI has called for a two-year pay freeze.