Ed Miliband says the protesters camped outside St Paul's Cathedral present a stark warning to the political classes and reflect a wider national crisis in confidence about the values of those in business and politics.

The Labour leader says that, while some have dismissed the cause of the protesters, they present a wake-up call, though they should not be allowed to dictate the terms of such a critical debate.

Writing in the Observer, Miliband describes the Occupy London protest and others around the world as "danger signals" that only the "most reckless will ignore". He says: "The challenge is that they reflect a crisis of concern for millions of people about the biggest issue of our time: the gap between their values and the way our country is run."

He adds: "I am determined that mainstream politics, and the Labour party in particular, speaks to that crisis and rises to the challenge". The Labour leader has until now made no comment on the furore around the protests, which have led to a debate about whether the camp should be forcibly removed.

His intervention will be regarded as a risky manoeuvre designed to hit home the theme of his party conference speech of a need to rid the country of "irresponsible, predatory capitalism". Miliband was widely praised after risking the wrath of some in the media by calling for Rebekah Brooks's resignation early on in the phone-hacking scandal at the News of the World and he will be hoping his comments today will chime with the wider electorate who he believes share some of the anger of those at St Paul's.

Miliband is careful to avoid endorsing the "long list of diverse and often impractical proposals" of the protesters. But he says their activities are a symptom of a wider crisis caused by record unemployment, rising inflation, squeezed living standards and turmoil in the eurozone which, he says, adds to the "sense that the economy is on the brink".

He says: "Certainly, few people struggling to makes ends meet and worried about what the future holds for their children will have either the time or the inclination to camp outside a cathedral. And many people will not agree with the demands or like the methods of the protesters. But they still present a challenge: to the church and to business – and also to politics."

The protesters settled on their current site three weeks ago yesterday after an initial plan to base themselves at nearby Paternoster Square, the private business and retail development housing the London Stock Exchange, was thwarted by an injunction. Since then the canon, chaplain and dean of St Paul's have all resigned amid confusion and indecision over whether the church should welcome the protesters or move them on.

Last Tuesday morning the Corporation of London was preparing to hand the camp a 48-hour eviction notice, but was forced to change its policy after the cathedral publicly backed the protesters. They have since been told that they will be allowed to continue to camp outside St Paul's until the new year.

While distancing himself from the methods and goals of the protesters, Miliband says this moment in time is similar to 1945, 1979 and 1997 in that a point has come where "business as usual is not an option". He says: "This is another of those moments because the deeper issues raised by the current crisis are too important to be left shivering on the steps of St Paul's."

The archbishop of York also criticised excessive salaries for top City executives, saying that large differences in income between rich and poor "weaken community life and make societies less cohesive". Dr John Sentamu said that excesses in the financial sector had helped to create big inequalities, "demonstrating how scandalously unfair our society is". He said: "If they [FTSE 100 chief executives] have a responsibility to their staff, it is hard to imagine a more powerful way of telling someone that they are of little value than to pay them one-third of 1% of your salary.

"Top pay has been found to bear little or no relation to company performance, but even if it did, isn't the performance of a company dependent on the work and wellbeing of all its staff?

"Among the ill effects of very large income differences between rich and poor are that they weaken community life and make societies less cohesive."