Mr Benson-Pope holds the safe Labour seat of Dunedin South but lost a tight selection battle for this year's election after he had to resign from the Cabinet.
Labour's candidate is Clare Curran, and the Otago Daily Times reported today there were rumours that Mr Benson-Pope was preparing for a tilt at the seat as an independent.
The third-term MP has previously indicated he would not stand as an independent, but the report said he was telling people that under MMP they could vote for Labour with their party vote, but give their candidate vote to anyone they chose.
Mr Benson-Pope told the paper: "My loyalty to the party is beyond question and I don't intend to change that."
He did not return NZPA's calls.
Mr English raised the issue in Parliament today, and said if Mr Benson-Pope urged people to vote for Labour it would amount to election advertising under the Electoral Finance Act.
That would mean it had to be authorised by the Labour Party, and if Mr Benson-Pope was standing against Ms Curran, the party wouldn't be happy, he said.
"It's not entirely clear how Mr Benson-Pope could legally stand as an independent and advocate a party vote for Labour," Mr English said.
"Mr Benson-Pope might face real difficulties if he was to campaign as an independent Labour candidate in Dunedin."
