Local authorities receive grants from central government based on population, and borough finance bosses estimate each "missing person” loses them £300 a year.
Councillors have expressed frustration at the Office for National Statistics over the issue, but finance and HR assistant director Ken Clarke said previous requests for a revision had "fallen on deaf ears”.
The last census, in 2011, estimated Telford and Wrekin’s population to be 166,600 – a five per cent increase on the 2001 figure.
In his 2019-20 budget report, Mr Clarke wrote: "We believe the ONS undercounts our population by around 4,000 people, which has resulted in a further loss of grant of around £1.2million per annum in recent years – a cumulative loss of over £8m for the period 2013-14 to 2019-20.”
At a meeting of the Finance and Enterprise Scrutiny Committee, Councillor Charles Smith said: "We aren’t getting the money we should be getting.”
The Labour member for Wrockwardine Wood and Trench asked: "What are we doing to get on to the ONS to remedy this? Are we continuing to fight for it?”
Mr Clarke said the council were arguing for the figure to be revised.
"I don’t want to be negative but it does seem to fall on deaf ears,” he said.
"The ONS has a national methodology, which it applies nationally.
"They believe in it. We think it disadvantages relatively fast-growing areas like Telford and Wrekin.
"We should reinvigorate our efforts to lobby the ONS. We need to make sure the population estimate is as right as possible.”
Muxton councillor Nigel Dugmore, who is also deputy leader of the borough’s Conservative group, asked: "Won’t the figure be corrected anyway when the next census comes along in 2021?”
Mr Clarke said: "I’m probably wrong, but I had heard there was a cost-saving decision made not to bother with a census.
"Nonetheless, when they collect a census it takes a long time for the figures to be interpreted and acted upon.
"It will be too late to correct it for 2021-22.”
The ONS today disputed the claims made by councillors.
An ONS spokesman said: "The methods underpinning the mid-year estimates were last reviewed in 2018 and this resulted in the population estimate for Telford and Wrekin being revised upwards by around 800.
The latest population estimate for Telford and Wrekin was 175,800 (mid-2017), and is subject to a confidence interval of around 4,000.”
Last December, constitution minister Chloe Smith published a White Paper about the next England and Wales census.
It confirmed the government’s intention to go ahead with a "mainly online” census in spring 2021.
"ONS has a target to achieve a 75 per cent online return rate,” the White Paper says.
"Nevertheless, it is recognised that there will be some people who prefer, or need, a paper questionnaire. Paper forms will be available to everyone who asks for them.”
By Alex Moore, Local Democracy Reporter