Lord Mandelson has told the Politics Show that he is "not for turning" over controversial plans to part-privatise Royal Mail.
Lord Mandelson, Business Secretary
In advance of the first Commons vote on the proposals next week and with nearly 150 Labour MPs opposed to the scheme, the Business Secretary said: "It is essential to do two things.
One, keep the Royal Mail in the public sector and we will but:
Secondly, make the changes that transform the business to enable us to sustain the better delivery service for the whole of the future.
Unless we bring about these changes, that the Hooper Review recommended, we won't be able to do that."
He added: "Mandelson and the Cabinet are not for turning."
And he accused the postal union of blocking the changes that were needed to modernise the Royal Mail.
He said: "They obstruct changes and can resort to strike action. Nothing will change until the attitude of the Post Office Union changes."
148 Labour MPs have signed a Commons motion opposing the plans.
If they all voted against second reading, it would be the biggest backbench rebellion against any Government on a matter of policy.
The Business Secretary also questioned the latest allegations on David Cameron's own expenses, saying that people might conclude it "has a nasty smell about it."
Watch the Politics Show on Sunday at 11:00 on BBC One.
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