LONDON, July 14 (Reuters) - Financial firm Markit said on Thursday it will publish a one-off "flash" purchasing managers' index (PMI) for Britain at 0830 GMT on July 22, providing an early steer on how companies have fared since the vote to leave the European Union.
Markit already publishes flash PMIs - essentially a preliminary reading - for the euro zone, Germany and France.
"We believe that the Flash UK PMI release will provide valuable insight to businesses, governments, policymakers and investors seeking to assess the immediate economic impact of the referendum," the company said in a statement.
The flash reading, based on more than 70 percent of the usual monthly responses, will not become a regular fixture and the full PMIs for July will be published as usual at the start of August.
The PMIs for last month, based mostly on data received before the June 23 referendum, suggested Britain's economy was expanding at the slowest rate since March 2013.
(Reporting by Andy Bruce, editing by David Milliken)