The Scottish Government has been forced to admit to a "serious" blunder in the way official statistics were recorded for offenders who breach their tagging orders.

Figures published last month showed the number of persistent missed curfews had soared by more than 60%, but yesterday it was revealed they had actually dropped by 7.6%.

The government receives data on restriction of liberty orders from Serco, the firm contracted by Holyrood to operate the electronic tagging system. The firm yesterday admitted that it had been supplying the wrong information to the government, and blamed the error on a "misunderstanding".

The government was criticised at the time for the reported failure rates and has now been in talks with Serco to ensure the correct process is in place.

Kenny MacAskill, Justice Minister, said: "This is clearly a serious error and led to accusations at the time that electronic monitoring is not working. It does however provide further evidence that community penalties can play an increasing part in our progressive penal policy. We already know that reconviction rates are much lower for offenders who are sentenced to community sentence orders as opposed to those given short prison sentences."

The number of breaches is 911 - not 1588 as indicated last month. The revised figure is a 7.6% drop from the 986 in 2005/06.

The error occurred in the recording of "level two" breaches - repeat but minor curfew violations. Serco had included the number of warning letters sent to offenders who had missed their curfew - but these letters in themselves do not represent a recordable breach.

The most serious order, level one, and is triggered by damaged or removed equipment, a missing offender or physical violence towards enforcement staff. These fell this year, but accounted for 73% of the total recorded.

A spokesman for Serco Ltd said: "There was clearly a misunderstanding between us and the government as to what exactly the figures were that were being requested."