HMRC has this morning published new advisory fuel rates.
Normally, fleets are given a month's notice of changes but Government officials have revealed that mounting concern within the industry has led it to announce an immediate change.
A spokesman said: "There is some concern in the fleet industry about the level of AFRs and the level of increases are significant, so although HMRC would normally expect to give a month’s notice (and will do so for future revisions) on this occasion we responded to unusual circumstances and agree for employers to apply the new rates during June if they are able and willing to do so.
"This line will be reflected on the website and in guidance given to staff."
The current rates were introduced on January 1.
For petrol powered company cars up to 1.4-litres, the rate is 11p per mile, rising to 13p per mile for cars between 1.4 and 2.0 litres.
For petrol cars above 2.0-litres, the rate is 19p per mile.
For diesel powered company cars, the rates are 11p per mile for cars below 2.0-litres and 14p per mile for anything above.
The rates, reviewed on January 1 and July 1 each year, are based on unleaded petrol at 102.1p per litre and diesel at 106.3p per litre.
The current average price for unleaded is 115.5p and diesel 128.8p.
New advisory fuel rates: