The Northern Territory needs to "squeeze more money" out of online bookmakers based in Darwin, according to senator Nick Xenophon, after revelations they oversaw more than $8.5 billion in bets last financial year but contributed $2.5 million in tax.

Since 2009 online betting companies based in the NT have enjoyed a low tax cap. The NT Government introduced the cap to keep other states, notably Tasmania, from attracting the industry.

Thirteen bookmakers are currently licensed in the Territory, including Tom Waterhouse, Centrebet, Bet365, Sportsbet and Luxbet.

Under the cap, each online bookmaker licensed in the NT paid 10 per cent of betting profits (bets wagered minus payouts) until they reached the cap, which was set at $250,000 for the past five years.

This financial year it doubled to $550,000.

Darwin is Australia's online betting capital, home to some of the world's biggest agencies.

The NT's tax laws are "an absolute gift" to bookmakers, Senator Xenophon said.

"They must be laughing all the way to their offshore bank accounts," he said.

"The Northern Territory government needs to squeeze more money out of these operators."

Bookmakers bring jobs and spend money: Giles

NT Chief Minister Adam Giles would not say whether online bookmakers were paying enough tax.

He said financial spinoffs meant the industry was crucial for the local economy.

A tale of two bookmakers TabCorp NSW Pays tax in New South Wales

Pays tax in New South Wales Has 99-year monopoly on pubs and clubs

Has 99-year monopoly on pubs and clubs Pays proportional tax with no cap

Pays proportional tax with no cap $1 billion made in betting profits FY14

$1 billion made in betting profits FY14 Paid $154 million or 15 per cent wagering tax in NSW FY14 William Hill Pays tax in Northern Territory

Pays tax in Northern Territory Only operates online

Only operates online Owns Tom Waterhouse, Sportingbet and Centrebet

Owns Tom Waterhouse, Sportingbet and Centrebet Estimated $210+ million in betting profits FY14 (estimate based on half-year profits)

Estimated $210+ million in betting profits FY14 (estimate based on half-year profits) Paid $750,000 or 0.35 per cent in wagering tax in the NT FY14

"What we're happy with is the economic multipliers that come through having these businesses in the Territory," Adam Giles said.

"It's not just about the level of tax that a bookmaker pays, it's also about the staff that are employed there, where they live, where they spend their money, their partners and their families."

Wagering company Tabcorp launched an attack on the online bookmaker industry at this year's annual general meeting, with chairwoman Paula Dwyer accusing the industry of cheating the racing industry and the public of vital revenue.

"It matters because gambling taxes are reinvested to communities through infrastructure and services and all gambling operators should pay their way," Ms Dwyer said.

Tabcorp paid a proportional tax rate with no cap, which saw it pay $154 million tax from its $1 billion revenue in NSW last financial year.

But Tabcorp has 99-year agreements with New South Wales and Victoria to operate exclusively in pubs and clubs.

The Australian Wagering Council which represents online bookmakers said Tabcorp owned the online betting agency Luxbet and received the same deal as all other bookmakers.

Chief executive Chris Downy described Tabcorp's argument as a "furphy".

"This whole issue about the there not being a level playing field is just a big whinge on Tabcorp's part," he said.

"If Tabcorp want to level the playing field then what they should do is relinquish their monopoly rights and open up the land-based bricks and mortar retail business to competition."

The newly elected Victorian Labor government has declared it will fight for consistent wagering tax laws across the country.

Tabcorp declined an interview.