EU referendum: Boris Johnson tells staff to back his stance
Boris Johnson's office has warned senior officials at London's City Hall not to speak out in favour of staying in the European Union.
An email from his chief of staff, Edward Lister, seen by the BBC, tells deputy mayors and senior advisers to "either advocate the mayor's position or otherwise not openly contradict it".
The Mayor of London has accused pro-EU campaigners of trying to gag opponents.
His spokesman said the ruling applied only to those on "official business".
Mr Johnson was "relaxed" about members of his team campaigning on either side in a personal capacity, the spokesman added.
The instruction, in an email sent on 4 March, was circulated just 24 hours before Mr Johnson accused pro-EU campaigners of trying to silence those arguing for Brexit who he claimed were being "crushed by the agents of Project Fear".
Repeating his concerns about ensuring open debate during the referendum campaign when speaking to the BBC on Monday night, the mayor said it was "wrong" that John Longworth, the former boss of the British Chambers of Commerce, had not been able to articulate his pro-Brexit views.
Mr Longworth was suspended and subsequently resigned after saying the UK's long-term prospects could be "brighter" outside the European Union.
The order from his chief of staff not to allow Mr Johnson's team to express their views or contradict him appears to contrast with the mayor's public statements on the importance of an open and public debate.
The email says it includes an attachment offering formal advice from the City Hall management team on what the GLA can and cannot do during the referendum.
The email highlights that the advice says: "Boris is entitled, as mayor, to adopt a public position on this issue and then, as with all other mayoral policies, to receive support from GLA officers in relation to that policy position.
"The advice also makes clear that GLA officers can, when not at work, express personal opinions (which be contrary to the mayor's views). Whilst this is the formal position for you also, I would expect, given your roles, you either to advocate the mayor's position or otherwise not openly contradict it."
The email also notes that because it is a referendum and not an election "you are all able to be involved in the campaign as you may wish (but without using the authority's resources for your personal activities)."
The mayor's official spokesman said: "The mayor is relaxed about any of his team of advisers in a personal capacity campaigning for or supporting either side in the EU referendum.
"He wants to see an open and inclusive debate, and recognises that some of his advisors have differing views to those he holds.
"In his role as chief of staff Ed Lister advised the team that as official mayoral policy is now to support the case for leaving the EU they are requested to support that position when undertaking official City Hall business."
The mayor's office said the advice was "in line with that issued by the Greater London Assembly's statutory officers".
Although his deputy mayors and senior advisers are political appointees, they are technically officials of City Hall so not subject to the same rules as elected representatives.
The City Hall decision will be seen as a contrast to David Cameron's, taken after pressure from Eurosceptic ministers, to allow members of the cabinet to campaign openly on either side.
In what one minister described to the BBC on Monday as an "bitter and bad tempered debate" within the party, decisions over the conduct of the campaign on both sides are under intense scrutiny.
Boris Johnson's public calls for open debate sit uncomfortably alongside his office's private demand for discipline.