Downing Street has defended Cherie Blair's role in chairing a series of policy seminars at Number 10.

Opposition parties voiced concerns over the role for Mrs Blair - accusing her of adopting a "Hillary Clinton-style" role.

Ms Clinton, the wife of US president Bill Clinton, came under fire in the US from some for apparently influencing policy from her position as First Lady.

As with Ms Clinton, Mrs Blair has a hugely successful career outside politics. She has also had political ambitions of her own - having contested a seat for Labour in the 1983 General Election.

The role at policy seminars comes after years in which there have been considerable efforts made to avoid any impression of Mrs Blair having any influence on government policy.

'Dating back to 1999'

Downing Street confirmed that Mrs Blair had chaired question and answer sessions at the end of lectures, but said she did not take part in discussion.

A Downing Street spokesman said: "It is nonsense to suggest that Mrs Blair has overseen a major Government transport summit.

"We are talking about a series of lectures concerning a wide range of subjects which have been hosted by the Prime Minister in Downing Street dating back to 1999.

"These are lectures not policy-making events or meetings."

Mrs Blair steps in to chair the question and answer sessions on occasions when the prime minister has to leave because of other business, the spokesman added.

'Not accountable to Parliament'

But shadow transport secretary Theresa May said: "Not content with advice from the Department of Transport and the policy unit, Tony Blair has now taken to seeking advice from non-elected individuals.

"It is a sad indictment of the Government when the prime minister clearly deems his wife to be a better policy adviser than he does his secretary of state for transport."

Liberal Democrat Norman Baker said: "Mrs Blair seems to be adopting a Hillary Clinton-type role.

"It looks like another example of the prime minister having friends - in this case family - who are not accountable to Parliament, stepping into policy areas."