The League Against Cruel Sports is to be "spoken to" by the Charities Commission for lobbying a top London company about its apparent sponsorship of a Westcountry hunt, after one of its members assaulted a League monitor.

Pro-hunt campaigners claim that asking a FTSE 250 company about its sponsorship of an event staged by the West Somerset Vale foxhunt went outside the remit of a charity.

The bizarre row began with a physical attack on a league employee and has ended up involving magistrates, an anonymous FTSE 250 company, the Charities Commission and the league's lawyers. The league itself said complaining to the Charities Commission showed "just how desperate" the pro-hunt lobby were.

In September, the hunt's whipper-in, David Bevan, was convicted of common assault. A court heard how he attacked league monitor and sanctuary manager Paul Tillsley in March this year, leaving him needing hospital treatment. The league then approached a FTSE 250 company, which it has declined to name, asking whether, in the light of the conviction, it wanted to continue its apparent sponsorship of the hunt's annual show. The league said the company responded within 24 hours to say it had never given permission for its name to be used, and had written to the hunt asking not to be associated with it.

Then, the Cirencester-based Campaign for Foxhunting stepped in, and complained to the Charities Commission that, in lobbying the company, the League Against Cruel Sports had stepped outside the "stated objects of the charity". It argued that, as the charities watchdog, the commission should step in.

The league had previously been warned by the commission over a campaign prior to the last general eletion that was deemed to be party political. The Campaign for Hunting's Tim Bonner said it had stepped out of line again.

"The charity has been very clear about the reasons for its campaign," he said. "It is targeting Mr Bevan, his employers and their sponsors because of an altercation with one of its staff members, which the charity seems to believe requires action beyond the police and the courts. This has nothing to do with any of the stated objects of the charity."

Now the Charities Commission has said it will be taking up the matter with the league.

Mr Bonner said: "This sort of thing must raise questions about whether LACS is really a charitable organisation."

The league's acting campaigns manager, Louise Robertson, said: "Most people will notice that a hunt employee convicted of assault while at work is not disciplined or condemned by his hunt or the pro-hunt campaign, and yet they embark on a strange campaign against us for daring to contact a major company to ask about its links to that hunt. It just shows how desperate the hunts, and in particular the Campaign for Hunting, are at the moment."