Kate Forbes' campaign manager has said she is to blame after an abortion rights group accused the Finance Secretary of lying. 

During the Channel 4 SNP leadership contest hustings, the minister said she had responded to a letter from Back Off Scotland about buffer zones after rival Humza Yousaf claimed she had not.

READ MORE: Humza Yousaf's no mudslinging vow has 'disintegrated' says Kate Forbes

However, the group took to Twitter to say that simply was not true. 

"Kate Forbes has just lied on national TV in response to Humza Yousaf. She has not responded to our letter," they tweeted.

Speaking to journalists after the debate, Ms Forbes said she approved a response earlier in the week. "I apologise. I signed off on it two days ago. I thought it had gone," she said.

Michelle Thomson, her campaign manager, said she was to blame for the blunder.

“I can confirm that Kate signed off the response and it was my error that it wasn’t sent until this evening. She spoke entirely in good faith as she always does.”