A contender for the leadership of the second biggest teaching union has challenged its acting general secretary to a US-presidential-style debate on policy.

Hank Roberts, the veteran campaigner for a single, merged classroom union, has asked Chris Keates, of the National Association of Schoolmasters Union of Women Teachers, to take part in a public debate as the deadline for branch nominations approaches.

Mr Roberts must obtain 25 branch nominations by October 18 to be eligible to contest the leadership battle.

Ms Keates, who has been acting general secretary since the death of Eamonn O’Kane earlier this year, has already won a unanimous nomination from the union’s national executive. She has also received written nominations from branches around the country supporting her candidature.

In a letter to Ms Keates, Mr Roberts has accused her of failing to answer questions about her attitude towards professional unity.

He said in the letter: “What will still be missing in this ‘election’, unless a candidate other than you, who is already on via the executive nomination, can obtain 25 nominations, will be an actual election by the members and a chance for the mass of ordinary members to hear and participate in a debate on key principles.

“Therefore I am proposing that the two of us have a public debate on the key issues that face the NASUWT and the teachers’ profession at the current time. Indeed I challenge you to do so. I am prepared to meet anywhere, at any time.”

Mr Roberts has also written to branch secretaries asking them to “be democratic enough” to inform members that he is seeking nominations to stand, and has outlined his willingness to attend meetings to answer questions.

The letter also says: “The main issue is, will there be an election? Will the leader of the NASUWT be an elected leader or an unelected one? Will the mass of the ordinary membership be able to have their say by democratic ballot on policies and principles; and in election platforms put to them?

“Will the new general secretary have an electoral mandate from the membership?”

Ms Keates said this week that she had no intention of taking part in a debate. She said: “The whole thing is a nonsense. This is not a US presidential election.

“My accountability is to the members and to the national executive, not to Hank Roberts. I went through a rigorous questioning from the executive and clearly satisfied any concerns they may have had before receiving their nomination.

“As deputy general secretary and recently acting general secretary, and as a member of the union since 1978, my role has been to promote the policies of the NASUWT. Everyone already knows what I stand for.”