A group of leading US internet providers have been told to show their “fast lanes” and premium services are any faster than ordinary internet access.

The office of New York’s attorney general has written to Verizon, Time Warner and Cable vision raising worries that subscribers mightn’t be getting the speeds advertised. In-depth info was requested by senior enforcement counsel Tim Wu by 8.

In letters to the state’s three leading internet providers, the attorney general requested them to validate claims their customers were getting the accessibility speeds guaranteed, particularly for premium services.

The attorney general’s office is seeking each supplier’s complete broadband customers since 2011, grouped by service amounts. In addition, it needs all disclosures to prospective or real customers about copies of web interconnection arrangements; substantiation for special speed claims; associated customer complaints; and web speeds since 2013.

After the attorney general’s review of records and answers, business officials would be invited in services and to discuss their broadband advertising practices, Wu wrote.

Cablevision including in FCC and internal evaluations” and its Optimum Online service surpasses advertised broadband speeds, told the Associated Press that it’d be happy to supply advice to the attorney general.

Time Warner Cable said it was looking forward to solving the issue. “We’re assured that we supply our customers services and the speeds we guarantee them,” said a spokeswoman. Verizon said it was assured in the dependable and strong Internet speeds it delivers to subscribers”.