The growing divide in the performance of secondary schools between the north and south of England should make us "worry as a nation", the chief inspector of schools has said.

Sir Michael Wilshaw told a conference that England "north of the Wash" was being neglected "with serious consequences for the future" - and he highlighted problems in Bradford during his speech.

Re-emphasising his warnings against the Government's plan for new selective schools, he said part of the solution was "leaders who want to develop a grammar school culture and ethos in the non-selective system".

Sir Michael, who heads the schools watchdog Ofsted, said: "We should worry as a nation about this growing divide between the north and the south after the age of 11.

"Let me be clear, I believe the north is being neglected, with serious consequences for the future.

"We should worry much more about Stoke than Sevenoaks. We should worry much more about Manchester than Maidenhead. We should worry much more about Bradford than Brighton."

Sir Michael was speaking at conference about the Northern Powerhouse at Huddersfield University.

He told delegates he rejected the argument that this north-south divide is related to relative poverty, pointing out that many northern primary schools are doing well, even in poor areas.

Sir Michael highlighted the performance of primaries in Redcar and Cleveland, which he said had suffered huge recent job losses but are out-performing even London schools.

He said: "So this is not about poverty, this is about expectations.

"Too many children who are doing well in primary schools in the north of England are then going on to secondary school and not doing as well."

The chief inspector said GCSE scores in Liverpool, Manchester and Leeds were below national average and places around these cities, including Rochdale, Oldham, Doncaster and Bradford were doing even worse.

But Sir Michael said some areas in the north bucked this "depressing picture of what's happening in the north", singling out North and South Tyneside, York, Blackburn with Darwen and Newcastle.

The chief inspector painted a picture of one unnamed northern secondary school he visited recently where he witnessed "very little mixed ability teaching, with bright children lolling about, bored and listless, in too many classes".

He said: "Worst of all, the senior leadership team, including the head teacher, appeared far too accepting of the status quo, without a coherent view of how standards could be raised."

Sir Michael told the conference the answer was better leadership by both governors and head teachers rather than more structural reform.

He said: "We need good leaders of individual institutions and groups of schools. We need leaders who want to develop a grammar school culture and ethos in the non-selective system."

Earlier this month, Sir Michael warned that the Prime Minister's plan to bring back grammars threatens up to 20 years of progress in the education system and could affect the UK's ability to compete with the rest of the world.

On Thursday, he told the conference there had been great improvements in state eduction in the last 40 years but he said: "Unless we narrow this regional divide, the great improvement that we have made over the years will stall.

"This is a wake-up call for government and for all our education leaders, north of the Wash."

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