Regulators are keeping a close eye on the internet as it is increasingly used as a campaigning political tool.
Mr Blair launched Labour's YouTube channel last week
The Electoral Commission and Ofcom are watching web campaigning - which is not covered by the rules of TV and radio.
This week both Labour and the Tories used YouTube and other sites to launch their party election broadcasts before they were screened on television.
Parties have been reminded to keep track of the costs of running sites used for the 3 May elections.
Paid-for political advertising on television and radio is banned in the UK - instead parties are allocated Party Election Broadcasts during the campaign period.
PEBs date back to the 1924 general election campaign when the three main party leaders would make 20 minute speeches on BBC radio.
These days they have a five-minute limit, but parties themselves often prefer broadcasts as short as two-and-a-half minutes.
The major parties' broadcasts are carried in "peak time" - between 6pm and 10.30pm.
The number smaller parties get depends on the number of candidates they field and their share of the vote in the previous election. Parties must contest at least one sixth of seats to be entitled to a broadcast.
But the internet, while subject to the laws of defamation and some self-regulation, is not bound by the same rules.
The Conservatives' election broadcast, shown on the BBC and ITV on Tuesday evening, was put on Facebook, Webcameron, and YouTube earlier that day in a deliberate attempt to break with tradition.
The party said it wanted to reach out to a wider audience for the broadcast - a link to which was also emailed out to Conservative members, campaigners and anyone who has signed up to various Tory websites.
Last week Tony Blair launched Labour's own YouTube channel to communicate directly with voters. The party says its own election broadcast - televised on Monday but previewed on YouTube on Sunday - has so far attracted more than 1,000 emails and 5,500 texts.
The Lib Dems, whose election broadcast goes out on the television on Wednesday evening, have used YouTube and their own site to broadcast election campaigns, speeches and interviews. All parties are also using social networking sites to get their message across.
The Electoral Commission said it was keeping an eye on blogs and other internet sites, but largely to keep track of election spending rather than the content and proliferation of the broadcasts themselves.
Guidance has also been issued to parties about their obligations to report the costs of setting up and running websites.
Anthony Eden during the first televised party political broadcasts in 1951
"We don't have any plans to review that guidance but we are obviously monitoring the websites of parties and blogs with the elections taking place in May," a spokeswoman told the BBC News website.
"In terms of our remit, ours is very much in terms of their reporting any costs so people can see how much has been spent setting up websites."
Ofcom believes that its remit under the Communications Act 2003 would not extend to any current website - but says that could change in the future.
Websites that include text, audio clips, pictures and an embedded screen to watch footage would be unlikely to fall under regulation - but a website broadcasting pictures which filled the full screen might be.
"If it looks and feels like television, it might well be subject to regulation," a spokesman said.
"We are definitely looking at it from the future policy perspective - but it is not something we are called to [investigate] on a day to day basis."
Smaller parties, which do not get as much coverage on television, have also recognised the benefits of broadcasting on the web.
The UK Independence Party is currently revamping its website and says it will be extending its use of internet broadcasts in the future.
"We are also advertising for someone to come and work in the press office just to run the official website and start a blog site for the leader," a spokesman said.
"Traditional outlets are still bound by very draconian rules and regulations, while on the web sites it's a free-for-all."
In 2004 the British National Party complained of "politically correct censorship" after Channel 5 refused to air its European election broadcast.
Now it has its own "BNPTV" section on its website and has posted its Scottish parliamentary election television broadcast on YouTube.
Meanwhile the Greens use their own website for official videos, although MEP Caroline Lucas also puts up clips of her speeches on YouTube.
The party's communications chief Jim Killock said it was also a good way to get local politics some airtime and said politicians tended to be more relaxed and "human" in web broadcasts.
He does not think that the proliferation of web broadcasts is making a mockery of party election broadcast regulations - as all parties have the same access to the internet.
"The reason those rules are in place on television and radio is because, when broadcasting was extremely difficult to get hold of, people wanted fair play," he said.
"I don't think you can expect that to be extended to the internet - it's a completely different scenario."
But all that could change over the next few years. The EU's audio-visual media services directive, which will increase the regulation of video content on the web, is due to come into force in 2009.
Ofcom added: "That will shake up the way we regulate and will bring many more services under the scope of regulation - but we are not there yet."