Mr Cameron said population was not a left or right-wing issue
The head of the new equality quango has heaped praise on David Cameron for his attempts to "deracialise" immigration.
Trevor Phillips, chair of the Equality and Human Rights Commission, heralded the Tory leader's speech as a turning point in the immigration debate.
He said Mr Cameron had set himself apart from Tories such as Enoch Powell, famed for his "Rivers of Blood" speech.
Mr Cameron on Monday said there were many benefits from immigration but the levels should be "substantially lower".
The Conservative leader said immigration had to be considered alongside other population pressures including people living longer, and more people choosing to live alone. He said his proposal to cut the level of immigration was nothing to do with race, but was because of the pressure on services such as schools, hospitals and housing.
Mr Phillips said: "For the first time in my adult life I heard a party leader clearly attempting to deracialise the issue of immigration and to treat it like any other question of political and economic management."
He said "it would be wrong of us not to recognise it as a turning point in British politics".
However, Mr Phillips, previously head of the Commission on Racial Equality, which has been superseded by the EHRC, told a conference in Birmingham: "Mr Cameron has a little way to go on this matter himself.
"He is asking the 21st Century question about immigration. But unfortunately, he is giving the 20th Century answer in proposing that all of these issues can be solved by capping numbers.
"Rather, we need to meet head on the challenges of rapid and diverse population growth.
"We need to find ways to capitalise on the injection of energy that new migrants bring and bolster our infrastructure and public services to cope with the new demands."
He said the test for Mr Cameron and all party leaders would come at next May's London mayoral elections.
"If decent politicians can resist the temptation to deal with the far right by moving on to their ground between now and 1 May, then the poltical air of our country next summer will be fresher and sweeter than it has been for a generation," said Mr Phillips.
In his speech, Mr Cameron argued that economic migration from outside the European Union, should be subject to annual limits.
And people from new EU countries should be subject to controls on access to the labour market - as the government has done for Romania and Bulgaria.
There are no immigration restrictions on people from existing EU member states.
Other pledges he made were to set up a border police force with powers to track down and remove illegal migrants and to raise the minimum age for spouses coming to Britain to 21, and ensure they can speak English.
He said that part of the attempts to cut economic migrants from outside the EU would involve making it a priority to get people "off benefits and into work".