Mumtaz Sattar, 38, from Port Glasgow, Inverclyde, lost her life in suspicious circumstances shortly after arriving in the Punjab with her husband Abdul eight days ago, and may have been throttled, according to a post-mortem examination.
It is now understood Mr Sattar, who was questioned by police about the death, has made a failed bid to get travel documents to return to Britain.
Aamer Anwar, the Glasgow solicitor acting on the dead woman's family's behalf, said Pakistani authorities have been told he should not be allowed to leave as he is the only witness to his wife's murder.
Mr Sattar said his wife died after the couple drank drugged tea before they were thrown out of a taxi they caught from Lahore Airport on September 22.
The post-mortem examination carried out in Pakistan found a bone in Mrs Sattar's neck, the hyoid, was fractured.
Mr Anwar said: "My understanding is that Mr Sattar's primary concern is to return to this country. And I have said on behalf of Mrs Sattar's family that if he wants his wife's killers to be caught, his primary concern should be to remain in Pakistan and assist the police with all their inquiries."
On Friday the officer in charge of the investigation in Pakistan, said he expected the case to be solved within days.
But Mr Anwar said things have gone on "go slow" and has called on the British authorities including the Foreign and Commonwealth Office, to put more pressure on the Pakistani authorities to ensure the family get justice.
A spokesman for the FCO could not comment on Mr Anwar's allegation and added: "We are aware of the death of the British citizen and are providing consular assistance to the family."