Eleven illegal migrants left the UK as a result of seeing vans with the message "go home or face arrest", the Home Office has claimed.
The advertising vans drove around six London boroughs where it is thought a lot of illegal immigrants live.
Plans to use the vans across the UK were ditched after they were condemned by critics.
A report by the Home Office attributed 60 voluntary departures to a wider campaign known as Operation Vaken.
This included newspaper advertisements and postcards in shop windows.
Of the 60 migrants who returned home in total as a result of Operation Vaken, 11 people left after seeing the "go home" advert vans, the Home Office assessment shows.
Twenty-nine left the UK after being warned of the risk of arrest through immigration advice surgeries.
But shadow home secretary Yvette Cooper, for Labour, described the vans as "divisive" and "a complete gimmick which should never have been approved by the home secretary in the first place".
The prime minister's spokesman rejected her comments, saying: "The right thing to do is look at a range of ways of tackling illegal immigration. This was one of them.
"It was piloted and then a decision not to proceed resulted on analysis of the pilot."
Immigration Minister Mark Harper pledged in a statement that the government "will continue to enforce the immigration rules and promote voluntary departure schemes to those who have no right to be in the UK".
In the written statement, Mr Harper said the voluntary departures represent a notional saving of £830,000, based on the average £15,000 cost of an enforced removal.
The pilot scheme, including the vans and other adverts, cost £9,740.
The number of texts received by the operation as a whole was 1,561 - of these, 1,034 were hoax messages.
The Home Office estimated that it took staff 17 hours to deal with the bogus texts.
Ninety-two phone calls were received, but 13 were hoaxes. Staff spent an hour dealing with the hoax calls.
Home Secretary Theresa May announced last week the pilot would not be rolled out further, conceding that the use of mobile billboards in particular was "too blunt an instrument".
Yvette Cooper said the Home Office evaluation of the pilot "proves this was never a serious policy to deal with illegal immigration which has been getting worse".
"It was a disgraceful personal error of judgement by Theresa May - she signed off the vans, the slogans and the funding and defended them for months before her recent u-turn.
"At the same time the number of people who were refused entry and then deported has fallen by 46.4%, its clear this is a government is failing on the fundamentals of illegal immigration."
Many Lib Dems have been openly critical of the campaign, with former Home Office minister Jeremy Browne telling members attending conference that the party would "not agree" to further use of the vans.
Secretary of state for Scotland, the Lib Dem MP Alistair Carmichael, welcomed the Home Office's latest statement.
"I have always been clear I did not want them repeated and have expressed my concerns about them. I am pleased we can now put this pilot behind us," Mr Carmichael said.
Earlier this month the Advertising Standards Authority banned the advert carried on vans, saying the arrest figures were misleading.
The advertising watchdog cleared the campaign of being offensive and irresponsible.