Lady Falkender - formerly Marcia Williams - was the personal and political secretary to Wilson during his premiership in the 1960s and 1970s.

She reportedly died of pneumonia on February 6.

One of the most powerful women in politics at the time, she came to prominence after Wilson's sudden resignation in 1976.

Lord Lipsey, who also worked as a political adviser in Wilson's government, paid tribute to Baroness Falkender.

The non-affiliated peer told BBC Radio 4's Today program: "She didn't have tremendous influence over policy matters but she had a general influence over Harold and she was his confidant - the person to whom he could turn when things were getting tough and get a comforting reply and perhaps he found common sense on occasion."

Asked if Wilson was scared of her, Lord Lipsey said: "We'll never know that because Harold's long dead and now poor Marcia is dead. She was a formidable personality."

It was claimed Lady Falkender drafted the former prime minister's controversial list of resignation honours, which became dubbed "The Lavender List", because it was written on lavender-coloured paper.

In 2007, Lady Falkender won STG75,000 in libel damages from the BBC over her portrayal in a drama-documentary which wrongly claimed she had compiled the honours list and that in doing so she included the names of people who had assisted her personally or from whom she hoped to receive assistance personally in future.

It also wrongly suggested that she had had a brief adulterous affair with Wilson and had subsequently used this to blackmail him.

Australian Associated Press