Samia Shahid, 28, from Manningham, Bradford, West Yorks, was allegedly killed and raped in Pakistan.
She had been travelling from the UK to visit her dad, who she had been told was seriously ill.
Muhammad Shakeel, who is on bail, was arrested three years ago for her alleged murder.
The case has not gone to trial, but police claim he had confessed to strangling Samia .
However, confessions obtained under arrest are not admissible in criminal proceedings in Pakistan.
“Samia was raped and murdered in an alleged honour crime three years ago.”
Naz Shah MP
Samia’s MP Naz Shah has now written to the Prime Minister of Pakistan after hearing the alleged murderer’s plan to return to the UK.
He is said to be seeking entry along with his new wife, who is British.
The Bradford MP said it was a “very worrying and very alarming situation”.
Shah added she hopes the new home secretary Priti Patel will block Shakeel’s entry to the UK.
Samia’s family arranged her marriage to her first cousin Shakeel in February 2012 in Jhelum, in the Northern Punjab.
She later obtained a divorce from Shakeel under Shariah law and married Syed Mukhtar Kazim in Leeds before moving to Dubai.
In July 2016, Ms Shahid received a telephone call, claiming that father was critically ill in Pakistan.
She flew to Islamabad airport against the advice of her husband, who believed the call was a lie.
Samia was then found dead at her cousin’s home in Punjab on July 20, six days after landing in Pakistan.
It was originally suggested she had died of natural causes, but police then launched a murder probe.
Her father, Muhammad Shahid, and Shakeel were arrested by Jhelum police and sent to jail on remand.
Police stated that Shakeel confessed to strangling Shahid in a statement on August 14.
Naz Shah MP wrote: “Samia was raped and murdered in an alleged honour crime three years ago.
“Despite the accused having spent two years in custody and subsequently being released on bail, the case has faced significant delay and sadly for the victim’s husband the justice and closure that is desperately needed is being denied.
“I am further being led to believe that Mohammad Shakeel (ex-husband), who remains on bail for the rape and murder of Samia Shahid is seeking to enter the UK having married another British citizen.
“Whilst no justice has been provided and no trial has taken place, this news is extremely worrying and potentially dangerous.”
Shah has sent copies of the letter to the Home Secretary Priti Patel and Foreign Secretary Dominic Raab urging them to make representation to their counterparts in Pakistan
Samia’s father was held as a suspected accessory to murder but released on bail., but died in January 2018.
Her second husband Syed, who she married in 2014, spoke in a BBC Two documentary last year about the loss of his wife.
He said he felt “helpless” as he dropped his wife at the airport before her “fatal” trip to Pakistan – fearing something was not right as family felt shame over the breakdown of her first marriage.