Mishcon de Reya is refusing to comment on its safeguard procedures after confidential information regarding the divorce of its client, Heather Mills McCartney, was leaked to the press.

The firm, which is acting for Mills McCartney on her dispute with ex-Beatle Paul McCartney, refused to comment on the leak of documents outlining Mills McCartney's case, with litigation partner Anthony Julius insisting no allegations had been made against the firm.

It is understood that after the initial press reports neither side's lawyers applied for an injunction on the document, containing allegations that McCartney mistreated Mills McCartney, which was leaked to the national press and published on 18 October. McCartney is being advised by Payne Hicks Beach family partner Fiona Shackleton.

Press reports have stated that the leaked document was an earlier version of the one filed in court last week.

Leading family lawyers told Legal Week it was becoming increasingly difficult for lawyers to make sure sensitive information was securely contained in high-profile cases.

Manches family partner James Stewart said: "If you have a very large team, including PRs, acting for one particular client, you are exposing yourself and the client to a higher possibility of a leak."

Hughes Fowler Carruthers family partner Ann Ison said: "It is matter of trusting your entire staff and making sure files are locked away. It is difficult to police. Documents could be intercepted at any point with emails being sent and papers going out to counsel chambers. [The leak] could have come from anywhere."

She added: "With the best will in the world, if you are working in a big office, one piece of paper could just go missing."

Dawson Cornwall children partner Anne-Marie Hutchinson added: "Over recent years, firms have had to be more stringent. [A case here] will only be worked on by specific members in the firm. We never use a temp as they could have been planted – I know of this once happening in a case at another firm."

The McCartney case is the latest in a series of high-profile divorce cases this year, which include insurance millionaire John Charman's £48m dispute with his wife and the House of Lords rulings in Miller and McFarlane, which strengthened the position of claimants divorcing wealthy spouses.