FINE Gael is highlighting the Seanad's failure to use its power to delay legislation as the referendum campaign enters its final weeks.
The new focus follows the damage done over the weekend to the party's claim abolishing the Seanad will save €20m a year.
The ad highlights the fact that the last time the Seanad delayed a bill was in 1964.
Mr Bruton denied the party was backing off the €20m figure.
“I think we have to use every dimension of the information that we have to get out there. There is obviously the cost dimension, there is an effectiveness dimension and today we are emphasising that,” he said.
Mr Bruton said the ad mobile will be driven around Dublin city centre all day, with a focus on the north side of the city, as GAA fans make their way to and from Croke Park.
"We are very keen to inform people about what the Seanad does and doesn’t do. And despite claims from the No side, the Seanad has very little power.
"In fact, it can only delay, not overturn legislation. And the last time it actually did so was in 1964. Those opposing this Referendum claim that the Seanad acts as an important watchdog; but what good is a watchdog that only barks every 50 years?" he said.