TONY BLAIR and Peter Mandelson last night led calls for Labour to reach out beyond its core voters if the party is ever to hold office again.

Their calls were backed by politicians in the North-East, including Mr Blair's successor, Sedgefield MP Phil Wilson, who said the party had to broaden its appeal.

As the party's soul-searching began after last week's crushing General Election defeat Mr Blair argued Labour should return to the centre and stand for “ambition and aspiration as well as compassion and care”.

The former Prime Minister wrote: “Hard-working families don’t just want us to celebrate their hard work; they want us to know that by hard work and effort they can do well, rise up, achieve. They want to be better off and they need to know we don’t just tolerate that; we support it”.

His views were echoed by Mr Wilson, who said: “We did not reach out beyond the core voters, such as those in the North-East, and we need to broaden the party’s appeal if Labour is to ever get into Government again.

“We need to win over the people who might not necessarily support us.”

He added: “I think Tony Blair is right and we need to reclaim the centre ground in politics and it’s the only way Labour will win an election”.

Leading Labour figures spent the weekend analysing the scale of the defeat, which saw the party almost wiped out in Scotland while failing to make significant headway in England and Wales.

Shadow health minister Liz Kendall today became the first MP to confirm she was standing for the Labour leadership, following the resignation of Ed Miliband, while potential rivals Chuka Umunna, Tristram Hunt and Andy Burnham are all believed to be weighing up possible bids.

Former Hartlepool MP, and architect of New Labour, Lord Mandelson accused Mr Miliband of throwing away a genuine chance of returning the party to power.

He said: “The awful, shocking thing about this election is that Labour could have won it or at least come a very near second.

“The reason we lost it, and lost it so badly, was because in 2010 we discarded New Labour rather than revitalising it and re-energising it and making it relevant for new times that we faced.

"That was a terrible mistake”.

But general secretary of the GMB union Paul Kenny warned against a move to the centre ground, saying: "The message about what Labour stands for - giving advantages in life and opportunities in life - was lost in the election campaign.

"Clearly a return to New Labour or anything like it would hardly win back Scotland."

Former minister Kevan Jones, Labour MP for North Durham urged party colleagues to take the fight to the Conservatives. He said: “"If the Tories go through with what they promised at the election it will have a massive effect on many of my constituents. We need to continue to fight in Parliament on behalf of the people that are going to be affected.

"We can't spend the next six months to a year talking to ourselves - we've got to get out there and take the fight to the Tories, as well as engaging with people”.

Labour MP Alex Cunningham, who increased his majority in Stockton North, said it was the SNP rather than Labour's message which was to blame for the defeat.

He said: "The Scottish Nationalist party won the election in Scotland and won it in England for the Conservatives. The Tories did very well selling the line that: 'the tartan terrors will cause havoc'.

Anna Turley, newly elected MP for Redcar which Labour won from the Liberal Democrats, said: "I spoke to a lot of people on zero-hour contracts or who were struggling to make it through to the end of the month and I felt we had something to offer them.

“But when I spoke to people more comfortably off they would say: 'well, what have you go to offer us?”