Martyn Jones is the former chairman of the Welsh affairs select committee
A Labour MP wants to hear Welsh Health Minister Edwina Hart allay patient fears over future neurological services in north Wales.
A review of services may mean patients have to travel to south Wales rather than nearby Liverpool for treatment.
Clwyd South MP Martyn Jones says the idea is "not acceptable" and wants Mrs Hart to explain the plans to the Welsh affairs select committee of MPs.
First Minister Rhodri Morgan attended its last session but not Mrs Hart.
In the past, Mrs Hart has said no patients will be "forced" to make long journeys and is expected to make an announcement on the issue next week.
The select committee is currently holding an investigation into cross-border public services.
Mr Jones's remarks, to BBC Wales' Dragon's Eye, were a rare attack by a member of Mrs Hart's own party.
At present, adult neurosurgery in Wales is carried out in both Cardiff and Swansea, but patients in the north of the country travel to a centre in Liverpool.
Around 600 in-patients from the region are treated by the NHS centre of excellence just over the English border each year, as well as a large number of out-patients.
But in 2006 a Health Commission Wales report recommended the creation of a single service in Cardiff.
Since that announcement, Mrs Hart has said that she wanted to ensure as many elective - non-emergency - operations as possible are carried out in the capital and Swansea.
The call has caused concern amongst neurological patients in the north, who fear they may face longer journeys than the maximum 90-minute journey to Liverpool.
Several meetings have been held across north Wales to discuss the plans but Ms Hart has said no decision has yet been made and no-one will be forced to travel to south Wales for treatment.
However, speaking on Dragon's Eye, Mr Jones said the plans still "frightened" many north Wales patients and called for Mrs Hart to come before the select committee and explain what the future held for his constituents and these services.
Patients in the north may have to travel to south Wales for treatment
"It's not acceptable to to travel three-and-a-half, maybe four-and-a-half maybe five hours from north west Wales down to Swansea and Cardiff when we have a centre of excellence just across the border," explained Mr Jones.
"This is actually frightening a lot my constituents that they may have to travel all that way when there's a very good centre in Walton which is half-an-hour from them.
"I don't think there should be any 'may' about it. At the moment there is a 'may' about it because we're having this review.
"Yes - it might happen but the only reason why we're considering it might happen is because of what was said.
"What I want to hear from Edwina Hart's own mouth is that in this particular area, where a lot of my people are really concerned, that she should come before our committee and say I didn't mean what I said or it's been misinterpreted - there will be no problem with neurological patients having to travel all the way down to south Wales."
The assembly government said: "The First Minister Rhodri Morgan gave evidence to the Welsh affairs select committee to answer all questions relating to assembly government policy and Ann Lloyd - in her capacity as head of the Welsh NHS - also gave evidence to answer more specific questions on the health service in Wales."