UBS has warned that the UK government's growth ambitions face a key test: whether they can be delivered without putting further pressure on public finances.
Dean Turner, an economist at the Swiss bank, identified three crucial areas for the economy.
They are closer ties with Europe, fiscal policy, and greater public control over essential services.
He questioned whether greater state involvement can reverse years of underinvestment.
Higher regulatory uncertainty and weaker private-sector participation could discourage domestic and overseas investment, he warned.
That could leave more of the investment burden with a state that is already under financial pressure.
"Redrawing the economic model that has defined the UK over the past 40 years raises important issues," said Turner in a note seen by Proactive.
"A greater role for the state, particularly in the provision of essential services, seeks to address some of the unintended consequences of privatisation.
"Underinvestment in key infrastructure is evident, and the economic costs are significant."
UBS expects speculation about higher taxes to persist, because the government has committed to its fiscal rules while fiscal headroom, the margin by which it meets those rules, continues to shrink.
Turner expects the Chancellor to use some of that headroom rather than rebuild the buffer immediately through tax increases, arguing that fiscal reserves exist for difficult periods.
He warned that the prospect of higher taxes could weaken incentives to invest and further undermine the UK's longer-term growth outlook.
On Europe, the economist said closer cooperation with the European Union appeared increasingly likely, although the UK was not about to rejoin the bloc.
Reducing non-tariff barriers could bring economic benefits, he said, but those gains alone would not resolve the UK's underlying growth problems.
Timing is another constraint, with several significant reforms due only after the next election, meaning 2030 at the earliest.
That makes it difficult for businesses and investors to plan around them today, he said.
UBS said convincing fiscal discipline could make higher gilt yields, the returns on UK government bonds, look more attractive, leaving the Budget as the key near-term test for markets.
