The Lib Dems could hold the balance of power in the Welsh Assembly if both Labour and Plaid fail to win an overall majority in the elections on Thursday.

But the Lib Dem leader dismissed any talk of a political alliance with Plaid Cymru until the nationalists made a clean break from separatism.

"The Lib Dems will not be party to any move that leads to the break up of the UK - forget it," said Mr Ashdown.

Nationalists 'not separatists'

Throughout this election campaign Plaid Cymru President Dafydd Wigley has insisted that his party has never advocated an independent Wales.

Dafydd Wigley: Confident of electoral success

Mr Wigley has said that Plaid's ultimate goal is "self-government in Europe".

But these claims have been ridiculed by the other parties who have accused Plaid of trying to tone down its language in order to avoid scaring off moderate voters.

They have even reproduced Plaid literature from past campaigns in an attempt to expose what they say is the party's separatist past.

'They are all over the place'

Mr Ashdown said Plaid previously had no difficulty in saying the party wanted separatism, now the party was saying something different.

"Where does Plaid Cymru stand is the key question. They are all over the place," he said.

"Their aim and purpose is separatism from the UK and they are trying to promote it as something else."

The Lib Dems, by comparison, he added, stood for "decent services and an assembly that will put the people first."

On the campaign trail in Wales, the party has revealed its strategy to cut the size of primary school classes.

Introducing 1,000 more teachers would benefit the quality of teaching pupils receive, the party claimed at a press conference in Cardiff Bay on Tuesday.

Plaid Cymru confident

Despite the attacks on its constitutional stance, Plaid remains confident of scoring its best ever electoral performance.

"After a long campaign, what we have seen is Plaid Cymru has won the hearts and minds of the people of Wales," said Mr Wigley.

"We have done our homework and we are ready to take the responsibility of government," he added.

"This is why we are redoubling our efforts from now until polling day.

"My appeal to the people of Wales is they turn out on Thursday and vote for a new beginning for our country.

"Plaid Cymru, the Party of Wales, has looked to this day since we were first founded."

Tories expect runner-up status

Meanwhile, the Conservative Party in Wales is forecasting it will come second in the assembly elections this week.

Rod Richards, the party's campaign leader, said the Tories had struck a positive chord with voters in Wales.

The party had run a positive election campaign and were confident of the outcome on Thursday, he said.

The Conservatives turned their focus to education on Tuesday, condemning Labour for failing Wales in the classroom.

Government pledges of an extra £800m for education in Wales was being spent on extra bureaucracy and advisers, claimed Mr Richards.