Johnson told MPs figure was £350m but sources say he made error in ‘car crash of an announcement’

The government has earmarked £1bn for safe cycling and walking routes in the next five years – not £350m, as Boris Johnson mistakenly told parliament in what one expert called “a car crash of an announcement”, the Guardian has learned.

But £1bn is still not enough to even build Greater Manchester’s 1,800-mile Bee Network of safe paths, according to its architect, Chris Boardman, a former Olympic cycling champion who is the region’s walking and cycling commissioner. He has asked Johnson for £1.2bn and says he will continue to do so.

“[The announcement] doesn’t change anything for me. I’m asking for what is required to deliver a network, not asking how much can we have. HS2 didn’t say: ‘How much can we have to build the rail network?’ – they’ve just said what the bill is going to be, ‘do you want to pay it?’ That’s the right approach,” he said.

On Tuesday the prime minister announced a £5bn fund to “overhaul bus and cycle links for every region [of England] outside London”. This, he said, would result in cyclists “enjoying hundreds of miles of brand-new separated lanes, with ‘mini-Hollands’ blooming like so many tulips in towns and cities right across the country”.

Details were vague but a government press release promised “over 250 miles of new, high-quality separated cycle routes and safe junctions”, as well as pilots of low-traffic neighbourhoods – the so-called mini-Hollands – which prioritise people over cars.

Asked in parliament by the Labour MP Ruth Cadbury – co-chair of the all-party parliamentary group for cycling and walking – how much of the £5bn would go to cycling, Johnson hesitated, looked at his notes and said: “In the first stage, £350m.”

The investment was described by Wera Hobhouse, the Liberal Democrat MP for Bath, as “a complete joke”.

Cadbury had prefaced her question by pointing out that it would cost at least £5bn to achieve the government’s ambition of doubling the rate of cycling from 2% to 4% of all trips.

But Johnson got his figures wrong, according to two sources in Downing Street. They insisted “at least £1bn” of the £5bn would be for walking and cycling, in addition to the £350m pledged in the Conservative election manifesto.

“It was a car crash of an announcement,” said one well-placed source. “We are pretty sure Boris made a mistake when answering that question and in fact it’s about £1bn for cycling now.”

Cadbury said she would be submitting a written question asking for clarification on the matter. “Until I see it in black and white I won’t believe it. All this confusion is symptomatic of the chaos No 10 operates in,” she said.

Rachel White, the head of public affairs at the walking and cycling charity Sustrans, said: “One billion is a step in the right direction but there is a long way to go to meet the government’s own ambitions and aims. Somewhere between £6bn and £8bn is what is needed to build capacity and capability in our walking and cycling networks.”