Liberal Democrat MP Julia Goldsworthy has called for tougher punishments for pubs and shops selling alcohol to minors.
A survey of 112 local authorities found that one in six pubs and shops were willing to sell alcohol to underage children and less than half of these received any punishment last year.
Venues in north-east Lincolnshire were the worst offenders in 2008 to 2009, with 189 venues out of 211 failing underage sting operations (89.6%).
Pubs and shops in Reading failed 53 out of 116 tests (45.7%), those in Bexley failed 29 out of 68 (42.7%) and Sheffield failed 17 out of 42 (40.5%).
Only two venues out of 62 tested in Middlesbrough sold alcohol to underage children (3.2%), one in 22 in Bath and north-east Somerset (4.6%) and five out of 106 in Dudley (4.7%).
Frequent testing in an area does not necessarily have a corresponding impact on the percentage of failure. Lancashire carried out the most sting tests of any authority in 2008 to 2009 and recorded a 16.2% fail rate.
Merton carried out the fewest, with 12 venues tested and none failing.
Overall, 11,169 tests were carried out across the UK, resulting in 1,967 failures.
As a result, 27 licences were revoked, 46 suspended and 105 licensees had conditions added to their licence.
A further 124 licensees were prosecuted and 532 were fined.
Tougher enforcement
However, Goldsworthy feels tougher enforcement is required. The Lib Dems want a one-strike and out rule, where every test failure results in a licence review.
"Too many shopkeepers are getting away scot-free with selling knives, cigarettes and alcohol to underage children," said Shadow Communities and Local Government Secretary Goldsworthy.
"We need to send a strong message to those who are ignoring these important age regulations. The limits are in place to protect children but if nothing is done to enforce them, the Government is failing in this duty."
Dennis Griffiths, licensee of the Miners Rest in Barnsley and president of the Federation of Licensed Victuallers Associations, said: "It's not the law that wants changing or made more severe, it's the police who need to enforce it."
He agrees with sting tests: "As long as they are done in the correct manner, they are fair."