This season's NatWest T20 Blast Finals Day registered the day's worst UK broadcast viewership since the competition began in 2003. Coming just a fortnight before county chiefs are expected to confirm ECB proposals that will preserve the existing structure of the competition, this news will intensify opposition to doing so.

According to the Broadcasters Audience Research Board (BARB), Finals Day at Edgbaston on August 29 attracted an overall average audience of 388,000 on Sky Sports - 159,000 for the semi-finals and 229,000 for the final programme between Lancashire and Northamptonshire. The figure is 10 per cent down on the previous lowest Finals Day in 2013, and 498,000 worse than the highest recorded in 2005.

When approached to comment the ECB was keen to point out that individual-day viewing figures are highly susceptible to rival attractions - such as in this instance: Mo Farah winning 5,000 metres gold at the World Athletics Championships, the third week of the Premier League football season and the launch episode of X Factor - and should be interpreted with caution. But in this case the figures are representative of a broader trend that has seen the past two seasons of the T20 Blast record the lowest average viewing figures as a whole in the competition's 13-year history.

Although aggregate attendances for this season's event totalled a record 827,654, a rise of 17 per cent on 2014 and Finals Day itself attracted a record attendance of 24,357, the competition's television appeal appears to be at best stagnating and at worst declining.

NatWest T20 Blast viewing figures ESPNcricinfo

The 2015 season saw 37 matches broadcast and a slight rise in average audience of 140,216, almost 3000 higher than 2014 but the two figures are considerably lower than the average across all 13 seasons and significantly lower than audiences recorded in the early seasons of the competition. Indeed, the average viewership of this season's final has been bettered by group-stage matches on 15 occasions in the past.

The ECB has reportedly tried to persuade its member counties to vote through a city-based T20 competition this season, thought to be favoured by broadcasters. But after facing considerable opposition to the idea the counties are likely to confirm ECB proposals for the existing structure to be preserved, albeit shifted to a block period in the school summer holidays. Historically TV viewership has been at its peak when the tournament has been played in a block rather than spread out across the summer as it has been in the past two seasons.

The current structure, adopted in 2014, was formulated on the back of an extensive survey of existing cricket fans which showed fans preferred regular Friday night scheduling of matches (which became known as "appointment to view") so that they could plan and budget for attendance. While this has increased the number of people watching live at the grounds it appears to have had a detrimental effect on television audiences.

The ECB was keen to reiterate the record attendances this season and boasted of a growing digital audience, with its T20 Blast-related video views exceeding 3.5 million. A spokesperson for the ECB reaffirmed the board's partnership with Sky, welcoming the quality and breadth of their coverage. Sky Sports meanwhile did not reject BARB's figures when approached for comment but pointed to a growing digital audience not included in BARB's data.

Given that the Big Bash League in Australia is now broadcast on free-to-air channel Network Ten, comparisons with the T20 Blast, broadcast on a subscription channel, would be unfair. However, it should be noted that before moving to Network Ten the BBL spent two seasons on Fox Sports where it broke Australian subscription records, registering average audiences of 282,000 and 233,000 in a country with a population roughly a third the size of the UK.

The impressive viewing figures on Fox improved Cricket Australia's chances of getting the BBL on to free-to-air television, which was achieved in 2013 when Network Ten signed a five-year deal worth $100 million.