The former vice-president's speech on Monday night at the Joe Louis Arena was part endorsement and part blistering attack on President George W. Bush, who denied him the presidency eight years ago.

'After eight years of incompetence, neglect and failure, we need change,' Mr Gore said.

'After eight years when our Constitution has been dishonoured and disrespected, we need changes.'

In 2000, Mr Gore won the popular vote but lost the disputed election to Mr Bush, who captured Florida and its electoral votes after a divided Supreme Court ended the recount of ballots.

Mr Obama stoked lasting Democratic anger over the 2000 outcome when he declared Mr Gore 'the winner of the popular vote'.

And on Monday night Mr Obama sparked raucous applause among the 20,000-strong audience by saying: 'You remember that.'

Mr Gore is one of the most popular figures in the Democratic Party, but stayed out of the primary campaign as Mr Obama fought a bitter battle for the nomination with rival Hillary Clinton.

However, on Monday he told the rally that while the primary was a contest between a strong and inspiring field of candidates, 'now we've made our choice'.

His wholehearted support could add lustre to Mr Obama's campaign as he tries to win over Democrats who backed Mrs Clinton, especially as he served as vice-president under her husband Bill Clinton.

In a further consolidation of the two camps, Mrs Clinton's one-time campaign manager has been designated chief of staff for Mr Obama's vice-presidential nominee.

Ms Patti Solis Doyle was fired by Mrs Clinton in February after Mr Obama won a series of primary victories.

Mr Obama is counting on a win in November, and brought Mr Gore along to help validate him among Michigan's Democrats, after skipping their primary because it violated party election rules.

Meanwhile, Mr Gore's appearance has triggered renewed speculation that he might form a joint ticket with Mr Obama.

He did not mention that possibility at the rally, saying instead that Republican candidate John McCain's 'age and experience' are not equal to Mr Obama's judgment, pointing to the Democrat's early opposition to the Iraq war.

Mr Gore also told the crowd: 'I feel your determination after two terms of the Bush-Cheney administration to change the direction of our country.'

He accused Mr Bush of myriad missteps, including a botched response to Hurricane Katrina, economic problems, foreign policy mistakes and allowing lead-tainted toys and poisoned pet food in from China.

'Even our dogs and cats have learnt that elections matter,' he said.

'This election matters more than ever because America needs change more than ever.'

ASSOCIATED PRESS, WASHINGTON POST