Optus has been taken to court for allegedly misleading and pressuring 20,000 of its customers to sign up to the National Broadband Network (NBN) — sooner than they were required to.

The Australian Competition & Consumer Commission (ACCC) commenced proceedings against the telco in the Federal Court on Friday.

The regulator claimed that Optus told these customers that the NBN was coming into their area, and existing internet plans — delivered through its Hybrid Fibre Coaxial (HFC) network — would be disconnected.

But the timeframes the telco quoted to their customers were sooner than what was contractually allowed to cancel their services.

Optus even told customers their services would be disconnected in as little as 30 days, the ACCC said.

"This is particularly concerning as Optus received a significant financial payment from NBN Co for each customer that moved from its cable network to the NBN," ACCC chairman Rod Sims said.

The regulator said this conduct occurred during an 18-month period between October 2015 and March 2017.

However, that is not the only complaint the ACCC has against Optus.

Anti-competitive conduct

It also alleged Optus misled customers, between October 2015 and September 2016, into thinking they could not sign up to NBN services from its competitors.

"Optus created the impression that its customers were required to obtain NBN services from Optus, when they could have chosen to switch to any internet service provider," Mr Sims said.

"We are also concerned that Optus cut off some of its customers' internet services when it had no contractual right to do so.

"Telephone and internet are essential utilities and it is unacceptable for Optus to treat its customers this way."

In response to these allegations, an Optus spokesperson said the company was "working cooperatively" with the regulator.

"The ACCC’s action today relates to past processes that we have successfully addressed."

"We also compensated customers who had been disconnected without sufficient notice."

This is the second time this week that the telco has been in trouble with the ACCC.

On Monday, Optus admitted that it misled more than 8,700 customers about the speed of their NBN plans, and agreed to compensate them.