Welsh political parties are launching their campaigns after Gordon Brown announced a general election for 6 May.
Voters in Wales will return 40 MPs, with several key seats.
Labour said it faced an "old Tory party of cuts", but Conservatives accused the government of planning a "tax on jobs" which could "kill" economic recovery.
Plaid Cymru said it was the only party putting Wales first, while Liberal Democrats said they offered a "different future" and change.
On Tuesday, Prime Minister Gordon Brown held a Cabinet meeting in Downing Street before heading to Buckingham Palace to ask the Queen to dissolve Parliament.
The campaign is likely to be dominated by the economy and spending cuts.
It's going to be a very tough fight for the future of Wales
Welsh Secretary Peter Hain, Labour
Welsh Secretary Peter Hain said this was very different from the last three elections when everyone expected Labour to win.
"Now everyone knows the Tories are in the lead, Labour are the underdogs," he told BBC Radio Wales. "It's going to be a very tough fight for the future of Wales.
"What is at stake here, especially in the key battleground seats which will determine the outcome of the election in Westminster is whether people vote Conservative or Labour. Only Conservatives or Labour can form a majority or minority government.
Mr Hain said Tories were "not being straight with people" and "their sums do not add up", describing an "old Tory party of cuts and right-wing policies".
He said Labour would "keep investing in front line services, in schools, health services and policing", and would secure the "fragile recovery".
The Welsh Conservatives launched their election campaign in Cardiff
Michael Gove, the Conservatives' shadow secretary of state for children, schools and families, said: "Certainly at the moment the momentum seems to be with the Conservatives, and particularly in Wales we're very confident that in a number of seats from Aberconwy to the Vale of Glamorgan that we are best placed to win.
"I think folk in Wales are genuinely worried about the state of the economy and the fragility of the recovery.
"There's a clear choice at this election: you can either vote for Labour and they will introduce a tax on jobs which we fear will kill the recovery or you can vote for the Conservatives and we won't implement that tax on jobs."
Mr Gove said the NHS was "our number one priority".
The very real prospect of a more politically balanced parliament means that we could have the influence to make the London government deliver a better deal for the communities of Wales
Helen Mary Jones, Plaid Cymru
"Across the UK, whether you are in Aberconwy, Bridgend, Vale of Glamorgan or Wrexham, the one guarantee you have with the Conservatives is that we will not cut health spending. There will be no change to the guarantee that if you're ill, or if a member of your family is in pain, the NHS will be there for you. Other parties aren't making that pledge."
Plaid Cymru accused Labour and the Tories of being "headlocked in a battle over which party can inflict the worst cuts on Wales".
Plaid said voters should "think differently about politics in order to protect jobs, schools and hospitals" and it was "the only party which will always put the interests of Wales first".
Political parties in Wales are launching their election campaigns
Helen Mary Jones, Plaid's director of elections, said the party had an "incredibly strong and dedicated team that is committed to getting the best deal for Wales".
"Every one of us in Plaid Cymru, whether that be elected politician, or party activist, is determined to take the fight to the London parties and stand up for the interests and values of Welsh communities."
She said: "The very real prospect of a more politically balanced parliament means that we could have the influence to make the London government deliver a better deal for the communities of Wales.
"A more balanced parliament is well overdue, and the eventual outcome could be a fairer system and a better deal for Wales.
If we want a future that is different, then in this election we must choose a party that is different
Kirsty Williams, Liberal Democrat
Welsh Liberal Democrat leader Kirsty Williams said: "First, we must ask ourselves whether decades of Tory governments and New Labour governments have made the lives of people in Wales better off. For millions of workers and families, the answer is no.
"Second, we must ask ourselves what kind of future we want. If we want a future that is different, then in this election we must choose a party that is different."
Ms Williams said her party was different from those "whose campaigns are bankrolled by militant unions and non-domiciled millionaires", which she said had "presided over some of the worst recessions and highest periods of unemployment in our history" and had "forced our nation to spend billions on an illegal war while our services and schools crumbled here at home".
She argued that if the Lib Dem vote increased from one in four at the last election to one in three at this, then her party "can lead the next government and we will deliver the change that works for Wales."
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