Mr Clark, 71, MP for Kensington and Chelsea, said in a statement that the operation was carried out on Bank Holiday Monday at King's College Hospital in London. His wife, Jane, said "everything is fine".
Mr Clark, whose diaries are among the best selling political books of recent years, was taken ill over the weekend while working at Saltwood Castle, his family home in Kent.
"If I can comport myself with the dignity and competence of Ms Mo Mowlam I shall be very satisfied," he said, in a reference to the Northern Ireland Secretary, who underwent a similar operation.
It was unclear yesterday whether the tumour removed was benign or malignant. Many brain tumours are benign but patients may be treated with radiotherapy following surgery as a precaution. This is what caused Ms Mowlam's hair to fall out. A malignant tumour, which is more serious, would be treated with chemotherapy as well radiotherapy.
The MP, who returned to the Commons at the last general election following his defeat in 1992, has been advised by his doctors to avoid all public engagements for the next three months.
The symptoms of a brain tumour include severe headaches, vomiting, loss of vision or seizures. He was initially taken to the William Harvey Hospital in Ashford and from there transferred to King's College Hospital where he would have had an MRI scan to reveal the tumour.
A spokesman for King's said Mr Clark had been transferred there because it was the regional centre for neurosurgery. He was operated on by consultant neurosurgeon Nick Thomas and discharged to his home on Thursday.
The operation, a craniotomy, involves drilling four holes in the skull over the tumour and then using a fine jigsaw to create a bone flap, which can be put back into place after the operation. Under the skull is tough, fibrous membrane that must be cut through to expose the surface of the brain.
Mr Clark has been one of the most colourful MPs of his generation, serving as an employment minister, a trade minister and a defence minister under Mrs Thatcher.
It was his role as minister for defence procurement that led to him becoming a key figure in activating the Scott inquiry into the arms-to-Iraq affair.
The Matrix Churchill trial collapsed after the defendants claimed that in 1988 Clark gave them a "nod and a wink" to carry on selling equipment despite the embargo.
He published his diaries in 1993, scandalising and charming Westminster in equal measure by revelations of his affairs and his frank assessments of many of his contemporaries.
Speaking at the family home yesterday, Mrs Clark said: "Alan is not coming out today. He's resting. He looks a lot better than he did before. He's just been advised to take a lot of rest and he certainly won't be coming out today or for some while, but everything's fine."Reuse content