By Andrew Osborn and Kylie MacLellan
LONDON (Reuters) - Prime Minister David Cameron touted his election victory as a strong mandate to renegotiate Britain's relationship with the European Union, as his party proclaimed on Monday a new-found unity over the traditionally divisive issue.
Following his unexpected securing of an outright parliamentary majority, Cameron told lawmakers from his Conservative Party that they had won a famous victory last Thursday but there was no room for complacency.
"We have got a mandate; it will be tough obviously but we have got a mandate," Cameron said of his planned EU renegotiation, before entering the meeting of members of Parliament to cheers, applause and the appreciative banging of fists on tables.
Cameron has made clear one of his priorities for his second term will be to reshape Britain's EU ties before holding a referendum by the end of 2017 on whether the country should stay in the bloc or leave.
The gathering took place in a wood-panelled parliamentary committee room overlooking the River Thames, off a corridor lined with the portraits of previous prime ministers such as Winston Churchill.
Had Cameron failed to win so emphatically, the room would probably have been the venue for a move against his leadership. However, his centre-right party can now govern alone following five years when it was in coalition with the Liberal Democrats.
Cameron was completing his cabinet line-up on Monday, promoting several women, two Britons of Asian origin, and a lawmaker with strong links to working class voters to demonstrate he is what he called a "one nation" prime minister.
DIVISIVE ISSUE
Since his re-election, Cameron has phoned several European leaders to discuss his planned EU renegotiation, which he has said will get underway soon.
Lawmakers said Cameron, Foreign Secretary Philip Hammond, and Chancellor George Osborne, would lead the talks.
The issue of Europe has split the Conservatives before and contributed to the downfall of two of Cameron's predecessors, Margaret Thatcher and John Major.
Cameron, who has said his preference is for Britain to remain in a reformed EU, is keen to avoid another split. But he has not ruled out an exit if he fails to get the changes he wants.
Osborne said after the meeting, which he described as "a massive moment of celebration", that the party was united, with even ardent Eurosceptic lawmakers such as veteran Bill Cash - who have caused so many problems in the past - now on side.
"We had great sights like Bill Cash pledging his undying loyalty and why this wouldn't be like previous parliaments," Osborne told reporters.
Alistair Burt, a Conservative lawmaker, said the party was determined to avoid further infighting over Europe.
"We know the damage that it caused," he told Reuters. "It didn't settle anything in terms of the country's relationship with Europe, all it did was destroy us. And the overwhelming sense is that we're not going to do this again."
SHOPPING LIST
Cameron hasn't outlined a full list of everything he wants, but has said he would like to tighten EU migrants' access to British welfare, win an opt-out from the idea of "ever closer" union inside the bloc, and make sure that decisions taken by euro zone states don't disadvantage the country.
Some EU officials and politicians have baulked particularly at the idea of re-opening the EU's founding treaties for Cameron.
He got a boost on Monday, however, when former European Commission president Jose Manuel Barroso said Cameron was now in a stronger position to reshape Britain's ties and that the bloc would give him some of what he wants.
Although content for now, some Eurosceptic lawmakers made clear their opposition to the EU was entrenched, suggesting the issue will not go away for the Conservatives.
"The referendum pledge means that whatever renegotiation we get, if we don't like it we vote to leave," said Eurosceptic Conservative lawmaker Jacob Rees-Mogg.
"For a time after the referendum people will accept the result," he added in a comment which suggested he thought most Britons would decide to stay in. "Not forever, but you would have thought for five to 10 years it won't be an issue."