The main contender to be the Tory candidate for the London mayoral race has urged Iain Duncan Smith to ditch Section 28.

Stephen Norris told a fringe meeting at the party's Bournemouth conference that the party should not attempt to find a compromise on the "thoroughly offensive" issue.

"It's wholly without the basis of decent Conservatism in the matter of any person's sexual orientation," Norris said.

"We should simply - and without qualification - abolish it. It is based on the thoroughly offensive notion that homosexuality is evidence of a lack of moral fibre."

Norris, who is widely tipped to be selected as the party's candidate against Ken Livingstone, urged the membership to build on Theresa May's warning that the party needs to modernise.

The millionaire former MP said Conservatives need to become relevant to voters by speaking their language and being "free from old bigotry".

In a broadside to traditionalists, he claimed the party could offer an alternative to Labour despite Tony Blair's occupation of the centre ground.

"There is an enormous gap to be filled in British public life by a party that doesn't have to wander off to the far right in order to differentiate itself from Labour but actually stands its ground on the sensible middle ground and shows how Blairite Labour has failed," he said.

In a hard-hitting speech, which called for the party to take radical steps, Norris said overhauling the party did not mean jettisoning the party's values.

He argued that the core principle of the right of the individual should focus on "equality of respect".

"In any modern democracy we ought to approach people as having equality of respect of whether they are male or female, young or old, poor, black or white, gay or straight," he told party members.

"Whether they came here a month ago or whether their family has been here for a thousand years.

"It's the only basis on which a decent society can be based."

He warned that the strategists overhauling ideas had to create a range of policies rather than focusing ideas on the particular concerns of one community group.

"If you can imagine that you can develop any coherent policy that attempts each of these minorities as an entity in itself then you will fail," Norris said.

They should focus on the issues crime, schools and healthcare which are important to minority groups as well as traditional voters.

"It allows us to be the party of the marginalized and the dispossessed but equally the party of the young, white, middle class couple," he said.

Norris warned the party had to be serious about change rather than hoping to tell voters what they wanted to hear in a bid to regain power.

"The message has to be quite simple. You have to believe in equality and you have to see it through from start to finish. You have to will as much the means as the ends," he said.

On the thorny issue of how candidates for parliamentary seats are chosen, Norris slammed the frontbench team as "ridiculously skewed".He argued that the aim had to be a parliamentary party that "looks like the whole country".

"I very much hope we can achieve that through a process of encouragement and advice with constituencies around the country. But let there be no question of this; if persuasion fails we should seek some other means," he said.

Norris was at pains to stress he was not attacking the leadership of Iain Duncan Smith - who, he believed, had made a good start at moving the party forward.

"If merely to articulate how the process of change takes place is to be regarded as an attack on our leader then none of us are going to make any progress ever," said Norris.

He admitted that on issues such as gay rights the party was decades behind its rivals where these issue had long since been integrated into core principles.

Norris argued that Duncan Smith, who became leader largely due to the support of the party's traditionalists, was the ideal person to usher them into the modern era.

"Only Nixon could go to China," said Norris. "Only Iain can go into new territory."