Tony Blair says the Egyptian army had no alternative but to oust President Morsi from power, given the strength of opposition on the streets. The military were confronted, writes Blair in the Observer, with the simple choice of intervening or allowing chaos.

The former prime minister's comments come as Egypt faces prolonged civil conflict after the removal from power of Morsi, who came to office with 51% of the popular vote at the country's first democratic presidential election, held last year.

As the Middle East envoy representing the US, Russia, the EU and UN, Blair's intervention will be seen as provocative among the region's Muslim population, which views last week's dramatic events as an indefensible coup organised by the Egyptian military establishment.

It also marks a striking development in the thinking of Blair, who now accepts that, in some of the world's more fraught regions, democracy will not necessarily deliver the kind of governments that can be defended in the face of overwhelming popular protest. Blair states that given the current situation in Egypt: "We should engage with the new de facto power and help make the new government make the changes necessary, especially on the economy, so they can deliver for the people."

He adds: "The events that led to the Egyptian army's removal of President Mohamed Morsi confronted the military with a simple choice: intervention or chaos. Seventeen million people on the streets are not the same as an election. But it as an awesome manifestation of power."

Taking a different approach to both President Obama and William Hague, who have expressed reservations over the military takeover, Blair makes clear that, overall, he believes it was the right move. "I am a strong supporter of democracy. But democratic government doesn't on its own mean effective government. Today efficacy is the challenge." Having taken this country to war in Iraq in 2003 despite huge public opposition, including a march by more than a million people through London, Blair now argues that shows of public unrest such as that in Egypt – fuelled and organised through social media – cannot be ignored.

"This is a sort of free democratic spirit that operates outside the convention of democracy that elections decide the government. It is enormously fuelled by social media, itself a revolutionary phenomenon.

"And it moves very fast in precipitating crisis. It is not always consistent or rational. A protest is not a policy, or a placard a programme for government. But if governments don't have a clear argument with which to rebut the protest, they're in trouble."

By Saturday night a total of 36 people had died and many dozens more had been injured in continuing clashes in cities across Egypt following the removal of the president.

The US state department urged Egypt's leaders to put a stop to the clashes, while UN secretary general Ban Ki-moon called for demonstrators to be protected.

Pro-Morsi protesters were gathering yesterday in Cairo's Nasr City area. The army, meanwhile, issued a statement on its Facebook page denying that some of its field commanders were putting pressure on the commander-in-chief to reinstate Morsi.

"These rumours … come within the context of the continued attempts to spread rumours and lies as one of the methods of the systematic information warfare being waged against the armed forces with the aim of dividing its ranks and striking at its strong cohesion," the statement said.

Blair says events in Egypt are just "the latest example of the interplay, visible the world over, between democracy, protest and government efficacy. Democracy is a way of deciding the decision-makers but it is not a substitute for making a decision." He launches a stinging attack on the Muslim Brotherhood's record in government, saying it was "unable to shift from being an opposition movement to being a government. The economy is tanking. Ordinary law and order has virtually disappeared," he says.

Blair also argues that the west needs to remain fully engaged in the region, including in Syria, Iran and Palestine. "This struggle matters to us. The good news is that there are millions of modern and open-minded people out there. They need to know we are on their side, their allies, prepared to pay the price to be there with them."

The central Cairo clashes erupted after a crowd of around 4,000, carrying banners backing Morsi, crossed the 6 October Bridge at sunset. They were met on an overpass near Tahrir Square by anti-Morsi demonstrators who had been celebrating at the ground zero of both of Egypt's latest revolutions.

Elsewhere in the country, clashes were reported in Alexandria and Luxor. There were also skirmishes in several rural governorates that had been strongly supportive of Morsi during his troubled and truncated year in office.