Charles Clarke says the UK has not made enough progress in fighting Afghan opium production after the UN stated cultivation was at record levels.
The poppy is Afghanistan's most profitable crop
The UN World Drug Report says poppy cultivation rose there by 16% last year covering 131,000 hectares.
Conservatives say the UK was given a key role in tackling the issue in 2001.
Tory David Davis accused ministers of failing, saying: "Heroin exported from Afghanistan makes its way through our porous borders into our communities."
War on drugs?
He said the problem fuelled escalating gun crime on British streets.
"It is no wonder the number of hard drug users in this country now tops a million people and is increasing," he said.
"Labour have not just failed in the war on drugs, they haven't even begun to fight it."
According to the UN the area under cultivation for opium poppies rose from 80,000 in 2003 to 131,000 hectares last year.
A Home Office spokesman said that G8 interior ministers agreed at their Sheffield summit earlier this month to increase resources to help Afghanistan with tackling drugs cultivation.
He said Britain had already given £70m over a three-year period towards countering narcotics.
The UN report said: "Of greatest concern is the fact that opium poppy cultivation has been introduced into previously unaffected areas and is now found in all 34 provinces of the country."