A female civil servant has accused Alex Salmond of trying to force her to re-enact a painting of an older man kissing a “scantily clad” woman by the Scottish painter Jack Vettriano.

The senior official, who cannot be named for legal reasons, said Salmond repeatedly grasped her wrists and refused to let go as he pulled her towards him, after an evening meeting at Bute House, the first minister’s residence in Edinburgh.

“He grabbed my wrists and pulled me towards him and I was quite shocked,” she told the high court in Edinburgh on Monday.

“I felt like every time I managed to get a hand off another hand would appear. He was very persistent and I felt like I was wrestling with an octopus. It just felt like hands, another hand, coming on to my wrist.”

Ae Fond Kiss by Jack Vettriano. Photograph: Jack Vettriano

Known as complainer B, her evidence came on the sixth, final day of the crown case against Salmond. The prosecution told the court it was dropping one of the minor charges of sexual assault against the former first minister and Scottish National party leader.

Salmond, who denies all the allegations, now faces 13 charges including one of attempted rape, one of intent to rape, two of indecent assault and nine charges of sexual assault involving nine women between 2008 and 2014.

During her testimony on Monday morning B said Salmond told her he wanted to act out a painting made by Vettriano for use as Salmond’s official Christmas card in December 2010. Called Ae Fond Kiss, it showed an older man in a suit and glasses kissing a woman in a red and white mini-dress, similar to a Santa Claus costume, under mistletoe.

B said she had earlier told Salmond, during a good-humoured business meeting to prepare him for first minister’s questions the following day, this card was “too sexualised” for the first minister and his wife, Moira Salmond, to send out.

“There were two individuals on the Christmas card, an older male who was taller, with glasses and a younger female with dark hair who was quite scantily clad,” she said.

B said Salmond was interrupted when one of his special advisers came up to the room, before he could kiss her, and she hurriedly left. She said she felt “quite alarmed” by Salmond’s behaviour but froze during the alleged assault, and was unable to cry out.

“I felt like my voice had gone so he just kept going. He was coming in to try to kiss me, in a way that I didn’t want to happen,” she said.

B said she went downstairs and told a junior female colleague, before reporting it to her line manager, but felt unable to make a formal complaint. She believed the civil service would protect Salmond. “I felt it would have been swept under the carpet,” she told the court. “I think I would’ve suffered in my career as a result. I never saw anybody in a senior position in the Scottish government tackle the first minister about his behaviour.”

Three senior civil servants who then served in Salmond’s private office later confirmed to the court that in late 2013 they introduced a new unofficial policy to ensure female officials were not left alone with Salmond after about 7 or 8pm.

Mike McElhinney, then a private secretary to the first minister, told the court they also discussed “withdrawing private secretary cover altogether under the circumstances” from giving Salmond support at night. “We were concerned about making sure the wellbeing of our staff was protected, and looked after,” he said.

They did not withdraw support but decided to change the office rota to ensure women were never alone with Salmond. They said this policy was never written down and did not launch any official investigations.

Joe Griffin, then Salmond’s principle private secretary, and the most senior official in the first minister’s office, told the court he and his closest colleagues first introduced this policy after a senior civil servant, known as complainer F, accused Salmond of forcing himself on top of her on a bed at Bute House.

Griffin told the court this approach had failed when they learned four months later that another female official, complainer G, accused Salmond of making sexual remarks to her after a meeting at Bute House, putting his arm around her and trying to kiss her.

Griffin said he then notified David Wilson, who was his boss and the Scottish government’s director for communications and ministerial support, about the incidents even though both women at the time said they did not want to pursue this officially.

Christopher Birt, another of Salmond’s private secretaries at the time, said he did not believe the women’s complaints would be properly dealt with. “I can’t speak for the women involved; I can speak for myself in that I wouldn’t have trusted the civil service procedures in place at the time [with] such sensitive issues,” he told the court.

The trial continues.