Prime Minister Gordon Brown leaving Buckingham Palace.

Gordon Brown fired the starting gun today for the most eagerly-awaited General Election campaign in nearly two decades.

The Prime Minister met his Cabinet before making the short journey up the Mall to Buckingham Palace to ask the Queen to dissolve Parliament.

On returning to Downing Street, he formally confirmed Thursday, May 6 as polling day – dubbing the election “the big choice”.

Launching the battle for a historic fourth Labour term in office – and the fight to retain his own Premiership – he warned voters the Conservatives could not be trusted to govern the nation.

Mr Brown outlined “three big challenges” facing the country – securing the recovery and tackling the deficit, while protecting front line public services.

He said: “This is an election not about small issues.“It is the big choice. The people have fought too hard to get Britain on the road to recovery to allow anybody to take us back to the road to recession.

“It’s too big a risk. It’s too great a danger. It’s too much of a threat.”

He promised one million new skilled jobs if Labour was re-elected and insisted Tory policies – in particular to reverse Labour’s planned increase in National Insurance contributions – would damage the economy.

And he told of how he would fight the election in the “cafes, canteens and front rooms” of the nation in a Barack Obama-style campaign by dropping in on workers and families for personal, one-to-one chats.

He added: “I have not spent the last two years taking this economy through the worst financial recession to sit back and allow a Conservative Party which has no idea about how to run the economy to put it all at risk.”

By contrast, Tory leader David Cameron staked his claim for the keys to Number 10 by championing “the Great Ignored”.

Casting the net far and wide in a bid to tap into what the Tories believe is disenchantment and disaffection with the Labour Government, he said: “We’re fighting this election for the Great Ignored.

“Young, old, rich, poor, black, white, gay, straight. They start businesses, operate factories, teach our children, clean the streets, grow our food and keep us healthy – keep us safe. They work hard, pay their taxes, obey the law.

“They’re good, decent people – they’re the people of Britain and they just want a reason to believe that anything is still possible in our country.

“This election is about giving them that reason, giving them that hope,” he added, before leaving London to travel to the West Midlands to visit key battlegrounds in Birmingham.

Issuing his own rallying call to supporters, he said the “new, modern Conservatives” had the “energy, leadership and values” to give the country a “fresh start”.

Laying down the battle lines for the Liberal Democrats, party Nick Clegg said today marked the “beginning of the end for Gordon Brown”.

He claimed Mr Brown was “directly and personally responsible for the biggest mistakes of the last 13 years”.

Mr Clegg, who is hoping to capitalise on polls that point to a hung Parliament, said the election was “wide open” with “people crying out for something new”.

The trigger for the showdown came as MPs returned to Westminster from their Easter break.

It marked the start of a mad flurry of activity and the Parliamentary “wash-up” period – the tying-up of the loose ends of legislation such as the Finance Bill, Digital Economy Bill and the Constitutional Reform Bill – until Friday, before the election campaign officially gets under way next Monday.