The government's plans for the future of Royal Mail are "comprehensive" and the most convincing option, the postal services minister has said.
Pat McFadden defended the decision to part-privatise the Royal Mail and rejected a campaign group's alternative proposal for the Postal Services Bill.
Compass called for a "more independent, arms-length" body which can borrow finances from the private sector and which brings in fresh management.
But McFadden branded the plans as "unworkable" and confirmed that the alternative proposals are not under consideration.
Neal Lawson from Compass told the BBC that the plans were designed to try and "find a way out of this mess".
He explained: "We have to preserve [the Royal Mail] and save it but we have to recognise that it faces a challenge of needing new investment, needing new management and needing a fresh start in terms of industrial relations.
"We agree with the government's analysis of the problems. We don't agree with its solutions. We have come up with an alternative that we think every Labour MP will vote for."
He added: "If you part-privatise it, all you do is lock in conflict with the union and the workforce. You will have the public against it and it won't work."
But McFadden dismissed the Compass proposals as a "political fix".
"The reason they did that was because it is really driven by the politics of finding a solution, around a political fix rather than the transformation that is needed for Royal Mail," he told the BBC.
He said that the government wants to keep Royal Mail publicly owned and to restore Royal Mail to health.
The government has come up with "a comprehensive plan to deal with Royal Mail's huge pension deficit, which we think we should for the sake of the hard-working men and women of Royal Mail".
"But this is only in the context where the taxpayer can have some reassurance that the company can be transformed for the future," he added.
McFadden admitted that the last week for Labour had been "difficult".
"But I don't believe it would be right in response to that to run away from the challenge of transforming an institution as important to the country as Royal Mail is," he said.
"In the end, we have to have a plan that is transforming for Royal Mail and isn't just a political fix ducking the problem.
"The plan is the most convincing plan that has been put forward so far.
"We have yet to hear an alternative that can transform the company in the way that the government's plan has."
The Communication Workers Union, meanwhile, has launched a John O'Groats to Lands End tour, taking to the public its case against the government's plans. A 20-foot high post box will journey across the country in a 12-week bid to build up support for the campaign against the government's plans.

Dods Parliamentary Communications Ltd