The depth of anger felt by Brawn at Jenson Button's move to McLaren was put on public display today when the team announced they would hold him tightly to the letter of his contract until the end of the year.

Button signed for McLaren this week after negotiations to remain with Brawn seemed to be dragging on for what the 29-year-old driver and his management team concluded was an excessively protracted period.

Brawn have responded in the only way remaining to them by forbidding Button even to take part in a press conference with McLaren, their sponsors or his new team-mate Lewis Hamilton until the end of 2009.

Over the years it has generally been the convention among Formula One teams to permit drivers who are leaving them at the end of any particular season to start working for their new employer after the final race of the year. As an example, Fernando Alonso was permitted to attend a Ferrari celebration day ahead of joining the Italian team at the start of 2010 despite being contracted to Renault until December 31.

Brawn, however, have insisted that Button will not be permitted to assume any duties for McLaren, whether on or off the track, before the end of next month. "Jenson will not be doing anything at all for McLaren until the end of this calendar year," said Nick Fry, the Brawn team's chief executive officer.

"And if he does, we will be looking on it very dimly. He didn't have any obligations to us in 2010, but there are issues with regard to the [McLaren contract] signing process on which we are in discussion with him at the moment. There are other constraints on what Jenson can do between now and the end of the year which we will be rigorously enforcing."

Fry had earlier claimed on autosport.com that Button had not received a better financial offer from McLaren and might even be moving to Brawn's Woking-based rivals for less money than the winners of the world championship constructors' title had tabled.

"I am actually earning less that I've been paid with Brawn," Button said on BBC Radio 5 yesterday afternoon said. "But things change and people move on. I always want a new challenge and I know that it is going to be difficult going up against Lewis.

"Either of the teams would have been able to give me a car capable of defending my world championship but I feel I need something else. It's definitely not for the money but because I want to experience something new."

Nevertheless, it is clear that Fry considers Button to have been disloyal over his new career move and concedes that they feared the possibility of doing a deal with him began to evaporate last weekend after his Friday visit to the McLaren headquarters, as revealed exclusively by The Guardian.

"Clearly loyalty would be nice," said Fry waspishly, "but in this day and age you don't expect too much of that. I am always happy when any employee leaves our company if they are going to a better job, and they always go with our blessing if that is the case. In this situation we don't see the logic of the decision and I think Jenson is going to have to up his game if he is going to beat Lewis on home territory."

It was reported tonight that Brawn have held preliminary talks with Michael Schumacher about a return to Formula One. The seven-time world champion is said to be a target for Mercedes, which this week took a 75.1% share in Brawn GP. Schumacher abandoned plans to drive for Ferrari last season because of a neck injury.