The 51-year-old, who represents the Scottish constituency of Caithness and Sutherland, was the only candidate when the five SDP MPs met to discuss a replacement for David Owen.

Mr Maclennan, who was originally opposed to the possibility of a merger between the SDP and the Liberal Party, currently under discussion, said he would follow the party majority on the matter.

He was opposed by three of the MPs who said there was no need for a leader as merger discussions continue.

But Mr Maclennan would not back down and his opponents conceded, on the basis that he understood he does not have majority party backing.

Speaking to the BBC Mr Maclennan said: "I can always be opposed if people do not like me personally.

"I have no doubt that the duty of myself at this time is to be the leader, if the party will have me, because I think we cannot have a vacuum at the top."

His role as caretaker leader was prompted by the walkout from the post by David Owen.

The party is split down the middle regarding the merger and those against the policy had hoped Mr Owen would return to the helm once it was out of the way.

Mr Maclennan has been pivotal to the SDP movement, using his expert knowledge of international law to draw up the party's constitution.

The Scottish barrister entered Parliament when he won his Scottish seat as a Labour candidate in the 1966 General Election.

In the early 1970s he was junior prices and consumer protection minister.

But he grew increasingly disillusioned with Labour policy including its pledge to hold a referendum on leaving EEC membership and the power of trade unions.

In 1981 he left to become a founder member of the SDP.

He joined the 'gang of four' - Roy Jenkins, David Owen, Shirley William and Bill Rogers.

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