The Silverstone race and the French Grand Prix at Magny Cours had been given only provisional dates in 2005, with the threat that both would be dropped unless a deal could be worked out to include them.
A meeting of team principals in a Heathrow hotel agreed to accept a limit of 24 days' testing between races next year - some teams tested for more than 40 days in 2004 - and the introduction of a single-tyre formula in 2006.
Both of these measures, particularly the latter, will save millions of pounds in the long term as the top teams, with the apparent exception of Ferrari, absent from yesterday's meeting, look for ways of reducing annual budgets in excess of £150million, reports the Guardian Unlimited website.
The deal sees an agreement by the nine teams present to accept a proposal from Bernie Ecclestone, the Formula One commercial rights holder, that they will compete in Britain and France for an extra $30million (£16.2milliion), shared among them.
The teams had wanted the usual payment of $40million for these two additional grands prix.
The teams are contracted to race in 17 grands prix. The addition of China this year increased the number to 18 and the inclusion of a race in Turkey adds another for 2005.
The British and French grands prix have become the "extra" events because of long-running problems over finance.
The British Racing Drivers' Club, the owner of Silverstone, must now decide whether to accept a one-year deal when, all along, it has wanted a two-year deal to allow time to arrange funding and planning permission for longer-term development of the Northamptonshire track.
"We haven't got a contract with Silverstone yet but I would be shattered and disappointed if we didn't get a deal," said Ecclestone.
