Read a full transcript of Heather Mills's GMTV interview

The sacking of Heather Mills by her lawyers Mishcon de Reya means that her divorce wrangle with Sir Paul McCartney is now all but certain to go to trial.

The loss of her lawyers means that Ms Mills may now have to act for herself in the complex negotiations unless she can find another law firm willing to represent her.

Unless she accepts the offer on the table — which looks unlikely — a trial is set for February.

A spokesman for Mishcon confirmed today that they were no longer acting for her but declined to say why or who had sacked whom.

But Ms Mills' recent outbursts on UK and US television, in breach of an agreement, at least pending the negotiations, not to make public comments about either the couple's marriage or their daughter, Beatrice, has effectively released the lawyers from their undertaking to act for her.

There has been speculation that Ms Mills lawyer, Anthony Julius, could not continue with the case for personal reasons after the tragic loss of his wife, the journalist Dina Rabinovich, from cancer ten days ago. But this is not thought to be a factor.

Rather, it is Ms Mills' recent behaviour, in defiance of both legal advice and an undertaking given during the current proceedings not to speak out, that has triggered the move.

Her intransigence in recent negotiations, described by one legal source as "very difficult indeed", would not have endeared her to the Mishcon legal team. But that alone would not have been reason for ceasing to act.

Lawyers for Sir Paul, who is represented by Fiona Shackleton at Payne Hicks Beach, declined to comment.

The stumbling block in the recent unsuccessful settlement hearing was the requirement by Sir Paul that his former wife agree not to discuss their marriage.

That was the price he required for a deal believed worth some £50 million, including a £20 million lump sum and annual payments for Beatrice.

Ms Mills in recent days has publicly blamed Sir Paul and his lawyers for blocking a settlement. But it is thought to be her own insistence on freedom to expose details of the marriage that is the barrier to a deal.

It is relatively unusual for solicitors to sack their clients; usually it is the other way round.

But a spokesman for the Solicitors Regulation Authority said: "This does happen — it is not uncommon. But while clients can sack solicitors at any time and for any reason, solicitors can only cease acting for a client with good reason, and usually with notice."

One such reason, she said, would be if the client had evidently lost confidence in her lawyers, and continually defied their advice or broke legal instructions or agreements.

"Clients are free to say, 'I don't accept your advice.' That alone is not sufficient to dump a client. But if a client has clearly lost faith in that he or she continually acts in a way that is contrary to what they believe is in her best interests, and particularly in breach of any agreements, then they could decline to act any more."

Under the solicitors' code of conduct, a solicitor can cease acting for a client "where there is a breakdown in confidence between you and the client and where you are unable to obtain proper instructions".

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