The BBC's role in the push towards universal broadband will encompass marketing, cross-promotion and provision of content to drive interest in taking up broadband.
It will also be asked to develop platforms with open standards available to all content providers and device manufacturers.
But the technology, communications and broadcasting minister questioned the £130m that has been identified as the likely surplus.
Although the figure was cited in Ofcom's conclusions to its second PSB review last week, Carter said he had heard “everything from zero pence to £380 million” in the course of his own inquiry.
He said that he would consider using the surplus for “other things” post-switchover, a possible hint that he could back Ofcom's suggestion of using it as a one-off payment to establish the proposed second PSB body.
However, he argued: “The debate about how to spend the money is significantly ahead of the progress. The successful completion of digital switchover is a long way from done.”
To date, the analogue signal has been switched off for 75,000 of the UK's 27 million homes.
Carter has set an “aspirational floor” of up to 2MBs broadband speed nationwide as the minimum for “credible and sustainable” access to video content, as PSBs continue to make more of their programmes available online.
He said there was no ceiling for broadband speed but that the target would be a base standard for the industry akin to the demands in place for utilities such as water and electricity.
He will also relax BT's commitment to provide universal telephony, which has been in place for 25 years, in recognition of the competitive market that has opened up in recent years.