Hull's three MPs have called on Boris Johnson and his government to meet their commitments to support councils after Hull received £2.6m less in coronavirus funding.
Hull West and Hessle's Emma Hardy, Hull North's Diana Johnson and Hull East's Karl Turner wrote the drop in funding left them questioning the government's commitment to local authorities.
It comes as Hull's share of the government's second round of £1.6bn in coronavirus funding fell to £7.2m from £9.8m in the first tranche, about a quarter less.
Communities Secretary Robert Jenrick said funding had been allocated in the fairest way possible.
Separately, Mr Turner wrote to the transport minister after the P&O ferry line announced more than 1,000 job losses, including on its Hull to Continental route.
The MPs' joint letter to the prime minister called on him and the government to ensure Hull City Council had the necessary funds to tackle the pandemic.
The letter stated: "The council has done an admirable job in the face of an incredible situation.
"They were heartened to receive assurances from your government that it recongnised the exceptional nature of the situation, that it would stand behind them and that they should not limit support or put off essential decisions because of finances."
"We now find ourselves in the unfortunate position of questioning that faith. "
The letter went onto state that Hull's funding had fallen despite Office for National Statistics (ONS) data showing it was the fourth most deprived area in the country.
ONS data also showed the death rate per head from coronavirus was twice the national average in deprived areas.
The government chose to allocate coronavirus funding based on per head figures in the second tranche after using a 'needs' formula for the first.
The letter stated: "These sobering statistics serve to illustrate the effects of the virus are far from uniform and underline the necessity for money to go where it is most needed.
"This is not simply a problem of 'cash flow' or 'additional costs' but also of the loss of essential revenue streams affecting longer-term financial sustainability.
"This is not a matter that can be left 'until the last minute' if the current vital level of service and support is to be maintained."
The Ministry of Housing, Communities and Local Government said in a statement a total of £3.2bn had been allocated to councils in England.
Funding was given to help local authorities deal with the immediate effects of the coronavirus outbreak.
The government would continue to work with councils on the best approach for the coming financial year.
Communities Secretary Robert Jenrick said the funding showed the government would continue to help councils during a "challenging" time.
The letter comes as Mr Turner also wrote toTransport Minister Kell Tolhurst MP warning that the loss of jobs at P&O Ferries would hit his constituency "incredibly hard".
Mr Turner wrote:
"There are now serious and well-founded fears that should these jobs go, they will never return.