The Liberal Democrats can widen their appeal to both Labour and Conservative voters, the party's leader in the Lords has claimed.

In an interview with ePolitix.com, Baroness Shirley Williams said the Liberal Democrats can extend their electoral base by avoiding "the politics of the past".

As the party's conference got underway in Brighton, the former Labour Cabinet minister said the issue will be at the centre of debate over the next four days.

"The huge attention of the press is on the question of how the Liberal Democrats are going to get themselves across in terms of major themes. How do they appeal at the same time to Labour voters and Conservative voters?" she said.

Williams argued the party can create distance from its political rivals by adopting a different approach, away from left-right thinking.

Instead it would focus on broad themes such as civil rights and the environment which are more likely to engage disillusioned voters.

"The traditional East-West compass has Labour to the left and the Conservatives on the right. The North-South compass point is the politics of the present time and it's all about fairness and democracy," Baroness Williams argued.

"If we look at the spectrum in another way, not the historical or economic way, then there is a whole world with a complete set of values that applies to a whole lot of people."

"Democracy is the devolving of power and fighting like hell to extend our civil liberties. We recently saw the use of anti-terrorism laws against protestors at the arms fair.

"With the environment, there's Swampy who will battle like fury and the National Trust which has thousands of members. The fact is they both have common values."

Williams quit Labour to help form the SDP in 1981 because of the party's swing to the left and internal feuds.

Today she claimed both Labour and the Conservatives are still wedded to central control and are increasingly authoritarian.

"Labour became a more authoritarian party because it was the way to deal with its hard left. Both IDS and Blair have become more authoritarian. We can be permissive in the Roy Jenkins tradition. That's a clear Liberal Democrat position that runs right across the two other parties," she said.

Baroness Williams said taxation would be the key issue on which the party would be scrutinised and argued policy would go beyond the "tax and spend" charged levelled by its opponents.

At its core would be a review of how much government revenue was spent on key public services such as the health service.

"We have to work through by looking at what are the core elements of the public services and which are ancillary. It's stripping away the essential from the non-essential," she said.

"There's no special argument for delivering three free meals a day in hospitals to those that can afford to pay.

"That kind of choice is where you have to work out what is part of the common good."

Liberal Democrats would also have to get across a strong but simple message to maximise its impact.

"The way forward is to limit the number of themes that we have to put across," she said.

This is part of the wider challenge for the party, she believes, if it is to build on the success of the Brent East by-election.

"There's a lot of people waiting out there. It's moving from a protest vote to a commitment vote. Turning it into something that will last into the general election and beyond. This is where the tide might turn. Brent East is a high water mark of where the tide could be," Baroness Williams said.

She also had some advice for Sarah Teather, who at 29 became Britain's youngest MP by winning the seat.

"She won a marvellous victory. It might be important to get a small team of Liberal Democrat supporters that could help on the range of issues that are going to come up like asylum and racial discrimination," she said.

Baroness Williams also warned that the death of Labour peer Lord Williams of Mostyn is a huge blow to reformers campaigning for radical change of the second chamber.

"He was a champion of modernisation in the Labour Party. The next challenge, as he saw it, was democratisation. Given Lord Falconer's hard line, it means we're going to have to fight very hard. In many ways it's a tragedy," she said.