Buenchico reaches for the Concise Oxford Dictionary, which gives the correct pronunciation of 'bath' as 'bahth'. Similarly, 'bath' should be pronounced 'bahth'. To me, that sounds remarkably similar to your ''barth' and 'parth'. (i.e. you seem to be objecting to the CORRECT pronunciation!).
While I accept that 'jewlerry' is wrong, the COD allows both the four-syllable 'jewellery' and the three-syllable 'jewelry', so it's not that far out.
If you want to listen out for a common error among TV presenters, try to hear all four syllables when they say 'Parliament' ;-)
Chris