The National Trust may be challenged in the courts over the way it conducted a members’ ballot on whether to ban trail hunting on its land.

The motion was defeated by a tiny margin at its annual meeting this month but now hundreds of members are claiming they were disenfranchised through not receiving ballot papers or getting adequate warning of the vote, according to Keep the Ban, which campaigns against bloodsports.

Trail hunting – when hounds and riders follow a scent path laid earlier – is regarded by many as a means of circumventing the 2004 Hunting Act. In the National Trust’s ballot, 30,686 members voted for a ban, while 30,985 voted against – a margin of 299 votes.

The Labour MP Andrew Gwynne is one member who says he was denied a vote. “The National Trust now needs to reflect on the deep concern of its members on how it has handled this issue,” he said.

Keep the Ban has engaged a barrister who advised it to petition the election courts over alleged voting irregularities. “Since last weekend we have been inundated with National Trust members informing us that they did not get an opportunity to vote or did not receive the magazine which contained the ballot papers,” said Keep the Ban’s director, Jon Proctor.

A spokesman for the trust said members had been told of the vote in the charity’s magazine. The AGM booklet, which includes ballot papers, is always mailed to members with the autumn magazine and published on the charity’s website, he added. “All members were invited to vote and the voting process was overseen by an independent scrutineer.”