NICK Clegg has set out his final conditions for any Coalition involving the Liberal Democrats with measures to spare public sector workers further pay cuts and efforts to protect the environment being non-negotiable issues.

But the Deputy Prime Minister refused to set as a red line opposition to David Cameron's pledge to hold an in/out referendum on Britain's membership of the European Union. Westminster-watchers believe he has not done that because in any coalition talks with the Conservatives, Mr Clegg could gain much leverage for securing Lib Dem policies in return for agreeing to a referendum in 2017, which the Tory leader has made clear would be a condition of his continued premiership.

The Lib Dem plans to break with the policy of pay restraint during the Coalition's term in office would mean a nurse on £25,000 would receive a minimum pay increase of £350, a police officer on £30,000 would receive £490 and a teacher on £35,000 would get at least £490 over the first two years.

Mr Clegg said: "Liberal Democrats will not enter a coalition with a party not prepared to back pay rises for people working in the public sector. They have paid more than their fair share and now enough is enough.

"The work they do is the cornerstone of a fair and decent society. We have a moral obligation to support them and protect the services they provide."

Thed Lib Dem leader said jobs and pay were under threat from the Conservatives. "They want to embark on a slash and burn approach to the public sector. And Labour's failure to deal with the economy, allowing austerity to drag on, will prolong pay restraint for many years to come."

He stressed: "Public sector workers have made enough sacrifices to help our country get back on track. Only Liberal Democrat MPs can guarantee an end to further cuts to pay."

Setting out his environmental commitment, the DPM said the Lib Dems had had to fight "constant trench warfare" with Mr Cameron and Chancellor George Osborne particularly on renewable energy and carbon emission reduction targets, where there had been "relentless, remorseless foot-dragging and resistance from the Tories".

Mr Clegg warned Labour leader Ed Miliband's flagship pledge to freeze energy prices could be part of his "green line" because the policy "will discourage billions of pounds of investment in exactly the kind of renewable energy technology that he claims he's interested in. It is clearly not consistent with a green approach to the economy".

The final conditions does not rule out the Tory plan for an in/out EU referendum.