There are "significant flaws" in the principles behind the government's crime reduction strategy, according to a report by an independent think-tank.
The British Crime Survey relates to convictions and not offending
The Crime and Society Foundation said it "stretched credibility" to claim crime was falling.
It criticised the government's use of the British Crime Survey as a measure, as it does not cover all offences.
But the Home Office said the government used statistics "appropriately" and had never claimed to measure "total crime".
The British Crime Survey (BCS) is compiled each year from interviews with 37,000 householders about their experience of illegality.
It does not routinely cover drug offences, sexual assaults, murders, fraud or crimes against under-16s.
The Crime and Society Foundation said by using the Survey to assess the success of crime-fighting policies, ministers risked ignoring those offences which aren't included.
The report said it was also "manifestly incorrect" to assert, as ministers have, that 100,000 offenders carry out half of all crimes - because the data relates to convictions and not offending.
Home Office minister Hazel Blears defended the use of the BCS.
Speaking on BBC Radio 4's Today programme, she said: "The BCS is accepted worldwide as the most authoritative basis on which we can track current crime and trends in crime over time.
2004 CRIME STATISTICS
Facts and figures with details of offences and regions
"We entirely accept that it does not measure everything in terms of crime.
"It measures big volume crimes - things that affect most people in their everyday lives, such as getting burgled, getting their car stolen."
And she defended the government's strategy of using the findings to target persistent offenders.
According to Ms Blears, the BCS showed that around 5, 000 prolific criminals were responsible for about ten per cent of all crime.
The Home Office minister said: "It is common sense to target the prolific offenders who cause the most harm to our communities."
And Ms Blears denied it "stretched credibility" to claim crime was falling.
"Crime is down significantly and that is accepted by the whole of the criminal justice community," she said.
The Crime and Society Foundation is based in the Centre for Crime and Justice Studies at King's College in London.