Addressing an audience during a lecture at the Royal Institute of British Architects, Cook said the last 20 years had seen a dearth of interesting architecture, and claimed that agenda is often placed above creativity.
"We're in a conservative period of British architecture," said the British architect. "I find that there is a narrowing of architecture; there are more schools of architecture that I've visited recently that have gone more narrow-minded."
Cook set up Avant-Garde architecture group Archigram in the 1960s, which put forward a series of radical proposals including a miniature capsule home and a city-airship hybrid.
But he said that this spirit of architectural experimentation is no longer present in the UK.
"There's not a spirit of adventure and discovery that there might have even been 20 years ago," he added. "I don't like to be a moaner but this is my honest view. Sometimes, dare I say, agenda is placed above creativity."
He claimed the awarding of contracts to "that dreaded phrase, a safe pair of hands" is stifling inventiveness. But he said that the UK had still managed to become a global force in architecture in spite of this.
"In the light of what I honestly feel is a rather dull period in British architecture, I don't think we're at our best – I don't think certainly in invention terms its the best period – but it's an amazing powerhouse," he said. "That's an odd paradox."
The talk took place as part of a programme of events celebrating Zaha Hadid becoming the 2016 recipient of the 2016 RIBA Royal Gold Medal.
Cook supported Hadid's nomination for the prestigious prize. In his citation, he praised the Iraqi-born British architect for her "impeccable eye".
"For three decades now, she has ventured where few would dare," he said.
Cook told Dezeen he is optimistic that the next generation of architects will include individuals that share this quality.
"I'm hoping that the very younger younger architects will become interesting again," he said.
Cook founded Archigram with Warren Chalk, Dennis Crompton, David Greene, Ron Herron and Michael Webb. The group won the Royal Gold Medal in 2002 – despite never having built a building together – in recognition of the influence their conceptual work has had on generations of architects.
Hadid became the first female architect without a male partner to receive the award this week – an event RIBA president Jane Duncan said was well overdue.
In a lecture of her own, Hadid said her projects – which include the Heydar Aliyev Center in Baku and London 2012 Olympic Aquatics Centre – are driven by an aspiration for architectural progress.
Cook currently runs CRAB studio with former student Gavin Robotham, following his curatorship of the 2006 Venice Biennale.
His comments about the state of British architecture follow another controversial speech he made during the World Architecture Festival 2015, slamming the redevelopment of London's Kings Cross as "boring, unbelievable, really dour".