Julian Assange's decision to seek asylum in Ecuador is "a tragedy" for the two women who have accused him of sexual assault in Sweden, their lawyer has said.

Claes Borgström, who represents the two unnamed women with whom the WikiLeaks founder had sexual relations in Stockholm in August 2010, told the Guardian the women were frustrated and disappointed by Assange's decision to seek asylum rather than face investigation in Sweden over claims of rape, sexual molestation and unlawful coercion.

"They are disappointed, but they are getting used to this by now," said Borgström, who has represented the women throughout Assange's sequence of appeals against extradition in the British courts.

"They know that all they can do is wait. I have told them I am not sure, but I think he will still be extradited … it is a tragedy for the women. I don't know how long it will take for him to be extradited now. Victims want to put these things behind them in order to be able to get on with their lives. The tragedy is that he doesn't take his responsibility. He should have come to Sweden."

The UK supreme court finally ruled last week that Assange must be extradited to Sweden under a European arrest warrant and his removal from the UK was expected within weeks. It was believed he was considering a final appeal to the European court of human rights, but on Tuesday night sought asylum at the Ecuadorean embassy in Knightsbridge, London, where he said he hoped for "diplomatic sanctuary and political asylum".

Marianne Ny, the Swedish prosecutor who had secured Assange's extradition in the supreme court in London, is following developments closely, said her spokeswoman, Britta von Schoultz. Ny would not comment on Assange's decision to seek asylum at the Ecuadorean embassy until he was in Sweden.

"It is solely a case for the British authorities to handle," Von Schoultz said. "When it becomes a case for the Swedish prosecutor, she will comment on the case."

Brita Sundberg-Weitman, a former head judge at a district court in Solna, a Stockholm suburb, who gave evidence in Assange's appeal against extradition in the UK courts, said she feared Assange's decision to seek refuge in Ecuador was misguided.

"I can understand that Assange is afraid of being sent from Sweden to the US, but I am not sure it will turn out well for him," she said.

"I don't know what his situation would be if he really landed in Ecuador and whether he would be safe. If you think of the policy of the Obama administration to kill whoever the president considers a terrorist wherever they are in the world."

She said there was considerable surprise in Sweden at Assange's move, adding she could not see how Assange could leave the Ecuadorean embassy in London without being arrested by the British authorities.

Borgström said he could not understand Assange's strategy. He said he did not believe the Ecuadorean government would find any basis on which to offer him asylum.

"I think when he leaves the embassy he will be arrested," he said.