Third runway decision: Theresa May braces for cabinet row as Heathrow announcement looms

Foreign Secretary Boris Johnson and Education Secretary Justine Greening are expected to attack any move to expand Heathrow

Prime Minister Theresa May is expecting a fight over airports expansion (Getty)

Theresa May is bracing herself for a Cabinet bust-up over Heathrow Airport ahead of an official decision on expansion tomorrow.

A Downing Street spokesperson admitted the Prime Minister would not have introduced a “special arrangement” for cabinet ministers to attack the final decision, if she was not expecting them to use it.

Boris Johnson and Justine Greening are expected to be among those speaking out, if the outcome is to build another runway at the west London airport as expected.

The decision will be made at a cabinet sub-committee meeting tomorrow morning, with Transport Secretary Chris Grayling due to report the result to the Commons afterwards.

The Prime Minister is allowing “exceptional and limited” dissent from some ministers to avoid a major cabinet split, but has set out tight restrictions on what they can and cannot say.

A No 10 spokesperson said: “Normally if you set out some special arrangements, you are doing that for a reason.”

Ms May will grant a “special derogation” allowing some ministers to speak out against the Government's plan, but no one will be able to “campaign actively” against the official position, nor “publicly criticise, or call into question the decision-making process itself”.

Ministers will also not be permitted to speak out against the Government in the House of Commons. To say anything outside the chamber, Ms May has told them they must “seek my approval”.

The No 10 spokesperson said no one had yet approached the Prime Minister to ask permission to oppose any expansion decision, but several ministers, including Foreign Secretary Mr Johnson and Education Secretary Ms Greening, are expected to tomorrow.

Neither are on the Economy and Industrial Strategy (Airports) Committee, chaired by Ms May herself, which will take the decision tomorrow. Among its nine members are the Chancellor Philip Hammond, Business Secretary Greg Clark, Commuities Secretary Sajid Javid and Mr Grayling.

After the meeting, the Transport Secretary will confirm the Government’s position in the Commons at about 12.30pm. It will then go to a full public consultation before a final decision is put before the House in the winter of 2017/18.

A third runway at Heathrow was recommended by the independent Airports Commission, chaired by Sir Howard Davies. But Tory Richmond Park MP Zac Goldsmith has said he is ready to quit and run as an independent candidate if the Government follows Sir Howard’s advice.