The former chief economist of the International Monetary Fund (IMF) has warned the cost of net zero will be "much more expensive than people imagine".
Speaking to the Lords Economic Affairs Committee, Olivier Blanchard said the expense of reaching net zero "has to be sent out" and paying for it purely through higher taxation isn't feasible.
The French economist told the committee said the "public does not believe, or has not been made to understand" the full cost of the transition, despite the Office for Budget Responsibility's estimate of £1.4trillion spent over three decades, but Mr Blanchard said the exact cost of reaching net zero remains unknown.
"It is going to be costly and that message has to be sent out," he told the committee, adding that there is a "substantial fiscal cost to achieve anything close to net-zero".
Continuing, Mr Blanchard said: "I think realistically we have to accept the fact that for a while it will have to be financed by debt, namely the primary deficit will have to be a bit larger as a result. I suspect that for the next few years, probably 0.5% more is the absolute minimum needed."
Net zero 'popular until people get asked to pay for it'
Sir Dieter Helm, a former advisor to Boris Johnson, told the Lords it would be "intergenerationally wrong" to "make the next generation pay by giving them the debt to replace the polluting system that we have run and polluted their environment [with]."
He added: "I have always maintained that a) we should do net zero, and b) it’s much, much more expensive than people imagine.
"The customers and the taxpayers are going to have to fund, in one way or another, costs greater than they assumed to be the case and they’re assumed by the OBR and by others because they get the costs of new technologies wrong and the direction of that error is very large."
Charles Goodhart, a founder of the Bank of England's Monetary Policy Committee, told the Lords committee: "The problem is that net zero is very popular until people get asked to pay for it."